my rigibody behaves weird

When i press Start in my Scene my Prefab kind of moves up in a very jerky manner.

Before start it’s like this:

however when i press Start it kind of jumps upwards. Heres a gif:

Im confident that its the unit that changes position and not the floor. the y-position increases by about 1.5. The unit also doesnt fall down despite gravity. When trying to move it in the inspector it behaves even more strangely but only on the y-axis.

Here are my settings for that unit:

I have already removed all my scripts and also played around with the rigidbody and character controller settings but nothing worked. Im not sure what else i could try out.

Simultaneous use of Capsule Collider and Character Controller is not recommended. Also in some cases child objects with colliders can cause similar situations.

Leave only the Character Controller and check the child objects.