07 h3 base model drivers side lumbar adjustment knob keeps popping off

[Happy Hummer]

I've looked at pictures of the replacement knob but they look identical to the one I already have. Meaning nothing looks broken o missing. So, what the heck is going on?
Does the seat adjustment unit have ears or tangs that are supposed to lock it in place?
Mine started literally falling off daily.

89042211
Part # for new.