Mouse sensitivity is messed up when looking around in a certain angle

I am working on FPS and today I’ve noticed while playtesting that moving the mouse feels weird.
When I turn around 360° at some point it feels like the sensitivity is increased (I turn faster around while moving my mouse at the same speed).
For example if I want to turn from 180° to 270° this part is faster than moving from 0°-180° or from 270° - 360°

I have no ideas why this happens all of the sudden. It confuses me even more because this only happens in one specific level. When I use the same character in a different level everything is fine. But I don’t know what can cause this issue.

Has somebody an idea?

edit:

I am using the Soul City assets to build a level. I deleted all assets from my level and suddenly the problem is gone. But I dont get why they would cause this issue. Is there a problem by having too many assets in one level?