Monitorian randomly fails on Dell UltraSharp

[Infi220]

I have two identical monitors (Dell UltraSharp U2412M): one connected via USB-C > DP, and another via USB-C > Mini Hub > HDMI > DVI-D. The latter never worked with Monitorian probably due to multiple adapters, but this report is not about that.

My issue is with the first monitor (USB-C > HDMI): whenever I launch Monitorian I randomly get one of these 3 results:

1. Works perfectly, both brightness and contrast.
2. Only the brightness slider shows up. Contrast slider is missing, even though the setting "enable changing contrast" is enabled.
3. An error message:

Monitor is not controllable. 
DDC/CI is not supported or enabled.

I usually need to relaunch Monitorian several times so that both brightness and contrast work. Could it be caused by Monitorian not waiting long enough for a response from the monitor when querying it?

Logs: https://drive.google.com/drive/folders/1gEmE2ukm5UcuUKfWcc8fTG2QmxynXDQv?usp=sharing

Operation log when the detection fails. The monitor in question is UID4352:

[Date: 11/27/2025 12:38:02 PM Ver: 4.13.0.0]
Display None

[Date: 11/27/2025 12:38:02 PM Ver: 4.13.0.0]
Display None

[Date: 11/27/2025 12:38:09 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:38:09 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:38:14 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:38:14 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:38:45 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:38:45 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:39:25 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:39:25 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:39:28 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:39:28 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:39:40 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:39:40 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:40:11 PM Ver: 4.13.0.0]
Initiated

[Date: 11/27/2025 12:40:11 PM Ver: 4.13.0.0]
Connectable by named pipes: True

[Date: 11/27/2025 12:40:13 PM Ver: 4.13.0.0]
ScanAsync [11/27/2025 12:40:11 PM]
{
  "Items": [
    {
      "Type": "UnreachableMonitorItem",
      "DeviceInstanceId": "DISPLAY\DELA07A\5&5600422&0&UID4354",
      "Description": "DELL U2412M",
      "DisplayIndex": 1,
      "MonitorIndex": 0,
      "MonitorRect": Empty,
      "IsInternal": false,
      "IsReachable": false,
      "IsBrightnessSupported": false,
      "IsContrastSupported": false,
      "IsPrecleared": false,
      "Brightness": -1,
      "BrightnessSystemAdjusted": -1,
      "Contrast": -1
    },
    {
      "Type": "UnreachableMonitorItem",
      "DeviceInstanceId": "DISPLAY\DELA07B\5&5600422&0&**UID4352**",
      "Description": "DELL U2412M",
      "DisplayIndex": 2,
      "MonitorIndex": 0,
      "MonitorRect": Empty,
      "IsInternal": false,
      "IsReachable": false,
      "IsBrightnessSupported": false,
      "IsContrastSupported": false,
      "IsPrecleared": false,
      "Brightness": -1,
      "BrightnessSystemAdjusted": -1,
      "Contrast": -1
    }
  ],
  "Monitors": [
    {
      "Item": {
        "Type": "UnreachableMonitorItem",
        "DeviceInstanceId": "DISPLAY\DELA07A\5&5600422&0&UID4354",
        "Description": "DELL U2412M",
        "DisplayIndex": 1,
        "MonitorIndex": 0,
        "MonitorRect": Empty,
        "IsInternal": false,
        "IsReachable": false,
        "IsBrightnessSupported": false,
        "IsContrastSupported": false,
        "IsPrecleared": false,
        "Brightness": -1,
        "BrightnessSystemAdjusted": -1,
        "Contrast": -1
      },
      "Name": "DELL U2412M",
      "IsUnison": false,
      "IsControllable": false,
      "IsConfirmed": false,
      "ControllableCount": 3,
      "IsByKey": false,
      "IsSelected": false,
      "IsTarget": true
    },
    {
      "Item": {
        "Type": "UnreachableMonitorItem",
        "DeviceInstanceId": "DISPLAY\DELA07B\5&5600422&0&UID4352",
        "Description": "DELL U2412M",
        "DisplayIndex": 2,
        "MonitorIndex": 0,
        "MonitorRect": Empty,
        "IsInternal": false,
        "IsReachable": false,
        "IsBrightnessSupported": false,
        "IsContrastSupported": false,
        "IsPrecleared": false,
        "Brightness": -1,
        "BrightnessSystemAdjusted": -1,
        "Contrast": -1
      },
      "Name": "DELL U2412M",
      "IsUnison": false,
      "IsControllable": false,
      "IsConfirmed": false,
      "ControllableCount": 3,
      "IsByKey": false,
      "IsSelected": false,
      "IsTarget": true
    }
  ]
}

Operation log when the detection succeeds and only brightness works (contrast is missing). The monitor in question is UID4352):

[Date: 11/27/2025 1:38:34 PM Ver: 4.13.0.0]
Initiated

[Date: 11/27/2025 1:38:34 PM Ver: 4.13.0.0]
Connectable by named pipes: True

[Date: 11/27/2025 1:38:36 PM Ver: 4.13.0.0]
ScanAsync [11/27/2025 1:38:34 PM]
{
  "Items": [
    {
      "Type": "DdcMonitorItem",
      "DeviceInstanceId": "DISPLAY\DELA07B\5&5600422&0&UID4352",
      "Description": "DELL U2412M",
      "DisplayIndex": 2,
      "MonitorIndex": 0,
      "MonitorRect": 0,0,1920,1200,
      "IsInternal": false,
      "IsReachable": true,
      "IsBrightnessSupported": true,
      "IsContrastSupported": false,
      "IsPrecleared": false,
      "Brightness": -1,
      "BrightnessSystemAdjusted": -1,
      "Contrast": -1
    },
    {
      "Type": "UnreachableMonitorItem",
      "DeviceInstanceId": "DISPLAY\DELA07A\5&5600422&0&UID4354",
      "Description": "DELL U2412M",
      "DisplayIndex": 1,
      "MonitorIndex": 0,
      "MonitorRect": Empty,
      "IsInternal": false,
      "IsReachable": false,
      "IsBrightnessSupported": false,
      "IsContrastSupported": false,
      "IsPrecleared": false,
      "Brightness": -1,
      "BrightnessSystemAdjusted": -1,
      "Contrast": -1
    }
  ],
  "Monitors": [
    {
      "Item": {
        "Type": "DdcMonitorItem",
        "DeviceInstanceId": "DISPLAY\DELA07B\5&5600422&0&UID4352",
        "Description": "DELL U2412M",
        "DisplayIndex": 2,
        "MonitorIndex": 0,
        "MonitorRect": 0,0,1920,1200,
        "IsInternal": false,
        "IsReachable": true,
        "IsBrightnessSupported": true,
        "IsContrastSupported": false,
        "IsPrecleared": false,
        "Brightness": 0,
        "BrightnessSystemAdjusted": -1,
        "Contrast": -1
      },
      "Name": "DELL U2412M",
      "IsUnison": false,
      "IsControllable": true,
      "IsConfirmed": true,
      "ControllableCount": 5,
      "IsByKey": false,
      "IsSelected": false,
      "IsTarget": true
    },
    {
      "Item": {
        "Type": "UnreachableMonitorItem",
        "DeviceInstanceId": "DISPLAY\DELA07A\5&5600422&0&UID4354",
        "Description": "DELL U2412M",
        "DisplayIndex": 1,
        "MonitorIndex": 0,
        "MonitorRect": Empty,
        "IsInternal": false,
        "IsReachable": false,
        "IsBrightnessSupported": false,
        "IsContrastSupported": false,
        "IsPrecleared": false,
        "Brightness": -1,
        "BrightnessSystemAdjusted": -1,
        "Contrast": -1
      },
      "Name": "DELL U2412M",
      "IsUnison": false,
      "IsControllable": false,
      "IsConfirmed": false,
      "ControllableCount": 3,
      "IsByKey": false,
      "IsSelected": false,
      "IsTarget": false
    }
  ]
}

Operation log when the detection succeeds and both brightness and contrast work correctly. The monitor in question is UID4352:

[Date: 11/27/2025 12:40:13 PM Ver: 4.13.0.0]
Display None

[Date: 11/27/2025 12:40:13 PM Ver: 4.13.0.0]
Display None

[Date: 11/27/2025 12:40:20 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:40:20 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:40:21 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:40:21 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:40:24 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:40:24 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:40:25 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:40:25 PM Ver: 4.13.0.0]
OnMonitorAccessFailed
Status: Failed
Message: 

[Date: 11/27/2025 12:40:33 PM Ver: 4.13.0.0]
Initiated

[Date: 11/27/2025 12:40:33 PM Ver: 4.13.0.0]
Connectable by named pipes: True

[Date: 11/27/2025 12:40:35 PM Ver: 4.13.0.0]
ScanAsync [11/27/2025 12:40:33 PM]
{
  "Items": [
    {
      "Type": "DdcMonitorItem",
      "DeviceInstanceId": "DISPLAY\DELA07B\5&5600422&0&UID4352",
      "Description": "DELL U2412M",
      "DisplayIndex": 2,
      "MonitorIndex": 0,
      "MonitorRect": 0,0,1920,1200,
      "IsInternal": false,
      "IsReachable": true,
      "IsBrightnessSupported": true,
      "IsContrastSupported": true,
      "IsPrecleared": false,
      "Brightness": -1,
      "BrightnessSystemAdjusted": -1,
      "Contrast": -1
    },
    {
      "Type": "UnreachableMonitorItem",
      "DeviceInstanceId": "DISPLAY\DELA07A\5&5600422&0&UID4354",
      "Description": "DELL U2412M",
      "DisplayIndex": 1,
      "MonitorIndex": 0,
      "MonitorRect": Empty,
      "IsInternal": false,
      "IsReachable": false,
      "IsBrightnessSupported": false,
      "IsContrastSupported": false,
      "IsPrecleared": false,
      "Brightness": -1,
      "BrightnessSystemAdjusted": -1,
      "Contrast": -1
    }
  ],
  "Monitors": [
    {
      "Item": {
        "Type": "DdcMonitorItem",
        "DeviceInstanceId": "DISPLAY\DELA07B\5&5600422&0&UID4352",
        "Description": "DELL U2412M",
        "DisplayIndex": 2,
        "MonitorIndex": 0,
        "MonitorRect": 0,0,1920,1200,
        "IsInternal": false,
        "IsReachable": true,
        "IsBrightnessSupported": true,
        "IsContrastSupported": true,
        "IsPrecleared": false,
        "Brightness": 0,
        "BrightnessSystemAdjusted": -1,
        "Contrast": -1
      },
      "Name": "DELL U2412M",
      "IsUnison": false,
      "IsControllable": true,
      "IsConfirmed": true,
      "ControllableCount": 5,
      "IsByKey": false,
      "IsSelected": false,
      "IsTarget": true
    },
    {
      "Item": {
        "Type": "UnreachableMonitorItem",
        "DeviceInstanceId": "DISPLAY\DELA07A\5&5600422&0&UID4354",
        "Description": "DELL U2412M",
        "DisplayIndex": 1,
        "MonitorIndex": 0,
        "MonitorRect": Empty,
        "IsInternal": false,
        "IsReachable": false,
        "IsBrightnessSupported": false,
        "IsContrastSupported": false,
        "IsPrecleared": false,
        "Brightness": -1,
        "BrightnessSystemAdjusted": -1,
        "Contrast": -1
      },
      "Name": "DELL U2412M",
      "IsUnison": false,
      "IsControllable": false,
      "IsConfirmed": false,
      "ControllableCount": 3,
      "IsByKey": false,
      "IsSelected": false,
      "IsTarget": false
    }
  ]
}

[emoacht]

Thank you for reporting.
But what I can say is that this app is designed to directly reflect the state of a monitor and your monitor is seemingly unstable.

[Infi220]

I appreciate the reply. Could you elaborate on what may be causing my monitor to be unstable? Do you think it's a problem with this particular Dell model? I have it connected through DisplayPort to USB-C on the computer. This seems like a very typical setup.

[emoacht]

I do not have any specific ideas, but you can try checking their connections by switching connectors and cables.