Frame loop for no apparent reason

[kasthack]

Describe the bug

Sometimes screen recording gets stuck with a few repeating frames after a few minutes.
This is reproducible with both renderers, so it's not a single renderer bug.

To Reproduce
Steps to reproduce the behavior:

1. Start recording with default settings.
2. Wait for a while.
3. Stop recording.
4. Open the resulting file in a player.

Expected behavior
Recording contains a timelapse.

Screenshots
Hmmm.

Desktop (please complete the following information):

• OS: win 10 x64

Additional context

Input: two 4k screens.