I recently upgraded from SW2019 to SW2021. Since then, I've had a strange behavior:

My assembly has no interferences (pic1)

However, when I turn on "move component" with "stop at collision" and pull down on the part called "knob" it tells me I've "started in a collided position" (pic2)


This is strange enough, but as I've tried to search for the mystery collision I've determined the following: If I move the part called "head" in the slightest (pic3), I become able to move "knob" without collision. This is particularly strange because 1) by visual inspection there are no parts in contact with "head" 2) I can move "head" with collision detection on and it finds no collisions 3) if I force head back to its original position with mates, the problem returns 

Assembly source can be downloaded from https://github.com/jostwald/beetle (it was too large to attach) The top level assembly is wing.SLDASM

 

Any help is welcome
thanks