[Bug] Library scrolling/layout breaks at certain window sizes

[IIDrippyJII]

Step 1. Pre-report Checklist

• I checked if there is already an open issue that described my problem.
• I checked if there is already an open issue at Millennium that describes my problem.
• I ticked the checkboxes without reading them.
• I checked the Update tab to see if there was an update.

Step 2. Theme configuration

Configuration

{
  "general": {
    "accentColor": "DEFAULT_ACCENT_COLOR",
    "checkForMillenniumUpdates": true,
    "checkForPluginAndThemeUpdates": true,
    "injectCSS": true,
    "injectJavascript": true,
    "millenniumUpdateChannel": "stable",
    "onMillenniumUpdate": 2,
    "shouldShowThemePluginUpdateNotifications": true
  },
  "misc": {
    "hasShownWelcomeModal": true
  },
  "notifications": {
    "showNotifications": true,
    "showPluginNotifications": true,
    "showUpdateNotifications": true
  },
  "themes": {
    "activeTheme": "Steam",
    "allowedScripts": true,
    "allowedStyles": true,
    "conditions": {
      "Steam": {
        "Achievement Notification": "no",
        "Add shelf button": "no",
        "Always show download bar": "no",
        "Always show game infos": "no",
        "Always show sidebar": "yes",
        "Banner Infos": "no",
        "Banner position": "Middle (default)",
        "Big Picture Mode button": "yes",
        "Bigger banner": "no",
        "Broadcast": "yes",
        "Darken not installed games": "yes",
        "Digital product info": "no",
        "Dynamic banner height": "no",
        "Follow the creators": "no",
        "Font": "Source Code Pro",
        "Footer": "no",
        "Friend icon": "no",
        "Friend list button": "no",
        "Game Overlay": "no",
        "Game cover shiny effect": "no",
        "Game info box artwork": "no",
        "Hide group chat": "no",
        "Info sidebar on right": "no",
        "Landing Header": "no",
        "Mica & Acrylic plugin support": "no",
        "Navigation buttons": "yes",
        "News button": "yes",
        "Notification button": "no",
        "Playbar in Banner": "no",
        "Profile pages header": "no",
        "Recommendations": "no",
        "Scrollbars": "no",
        "Sidebar on left": "no",
        "Sidebar on right": "no",
        "Sidebar only on hover": "no",
        "Steam VR button": "no",
        "Steam-Custom-Artworks Support": "no",
        "System accent colors": "no",
        "URL bar": "no",
        "VAC-Ban visibility": "Show",
        "Wallet balance": "no",
        "What's New": "Compact",
        "Window Controls": "Show",
        "Write a Review": "no"
      }
    },
    "themeColors": {
      "Steam": {
        "--st-accent-1": "102, 108, 255",
        "--st-accent-2": "135, 140, 255",
        "--st-background": "10, 10, 10",
        "--st-blue": "75, 137, 239",
        "--st-blue-hover": "100, 154, 242",
        "--st-color-1": "17, 17, 17",
        "--st-color-2": "30, 30, 30",
        "--st-color-3": "20, 20, 20",
        "--st-color-4": "24, 24, 24",
        "--st-color-5": "38, 41, 44",
        "--st-color-6": "38, 38, 41",
        "--st-green": "36, 166, 90",
        "--st-green-hover": "39, 185, 100",
        "--st-red": "240, 74, 74",
        "--st-red-hover": "242, 99, 99",
        "--st-yellow": "239, 141, 75",
        "--st-yellow-hover": "239, 141, 75"
      }
    }
  }
}

Step 3. Describe the issue

When using SpaceTheme, the Steam library scrolling/layout becomes unstable at certain non-fullscreen window sizes.

While scrolling down, game entries visually shift/move around in the grid/list.
Scrolling upwards can also become extremely fast/jittery.

The issue disappears when resizing the Steam window slightly larger or when using fullscreen mode.

The issue does not occur with other Millennium themes.

Step 4. How to reproduce

1. Open Steam in windowed mode (not fullscreen)
2. Resize the Steam window to a smaller size
3. Open the library and scroll
4. Observe shifting game entries and unstable scrolling behavior

Anything else?

• No additional Millennium plugins installed
• Steam restart did not fix the issue
• Another Millennium theme works correctly
• Issue seems related to specific window sizes/responsive layout behavior