The reminder keeps blinking for unlimited time if user activity is stopped <5s before deadline in Reading mode

[vedgy]

Describe the bug
In Reading mode, when the user stops mouse/keyboard activity between 25 and 30 seconds after the reminder appears, the reminder keeps blinking until the user resumes mouse/keyboard activity. The reminder window may keep blinking for a long time if the user leaves the computer or looks away for some time.

To Reproduce

1. Activate Reading mode. I cannot reproduce this bug in the non-Reading mode.
2. Wait till Micro-break or Rest break reminder appears.
3. Move the mouse or type for 28 seconds, then stop all mouse and keyboard activity.
4. The reminder reaches "Disappears in 0:00" but keeps blinking until the user resumes mouse or keyboard activity.

Expected behavior
The scheduled break starts 5 seconds after the user activity stops.
If starting the break at this point is difficult to implement, at least the reminder window should disappear when "Disappears in 0:00" is reached.

Screenshots
When the bug occurs, the reminder window keeps alternating between these two views:

Linux

• Distribution: Manjaro
• Distribution Version: stable with latest updates
• Desktop Environment: Xfce
• Workrave Version: 1.10.45; 1.10.48

Additional context
This issue has been annoying me for months or even years. I don't think that it is a recent regression. I have found the relevant code in BreakControl::heartbeat() but have trouble figuring out what causes the bug.

[GGGomer]

This issue also exists on:
OS: Windows 11
Version: 21H2
Build: 22000.856