It's unclear what is weird about it.
If you pinch zoom out you get zoomed out. In this case, the zoom resets back to being zoomed in when there is one finger touching the screen. Additionally, the single finger touching the screen is no longer registered as you are unable to move the map around anymore after the bug occurs.
I'm not able to reproduce any of this on my phone. What browser do you have? What OS and what version?
It is difficult to reproduce and doesn't bug out all the time.
I'm on pixel 6 pro running android 16.
Manager version is the latest google play release: 5.2.0
Here is another demonstration video, the first half shows expected behaviour and the second shows the bug: https://youtube.com/shorts/CTNUP-piivg
Can you reproduce it using this example?
https://maplibre.org/maplibre-gl-js/docs/examples/view-a-fullscreen-map/
I've been spinning maplibre map for a couple of minutes and I wasn't able to recreate it.
Sounds like it might be some weirdness of Flutter WebView.
Would it be possible to fix this on my client side?
Very unlikely we can fix it ourselves. It's not even clear what the issue is exactly and how to reproduce it consistently.
Weird behaviour can be observed when using two finger pinch zoom and rotate with one finger still touching the screen. This usually happens when fully zoomed in as can be seen from the demonstration video: https://youtu.be/7zLTy_dCjnk