Animation doesn't rotate object in playmode

Hey. I just made an animation which transforms an object, in this case an arm and the settings of a child of it. It all works perfectly in the Scene view but in play mode the arm doesn’t move. The animation is loading since the settings of the child are changing but the arm isn’t rotating. I also can’t rotate it manually in the scene view while in play mode. (I can if the animator is deactivated.) but i can scale and move it.
There are no scripts accessing the arm.
There is an idle animation looping on one of the children but i already deactivated it so it doesn’t seem to affect it.

The arm movement is essential for this animation so i have to get this to work…

Update: If i press play in the animation window while in play mode it also works. But just not through code…