Hello,

I have isolate the problem here (attachment).
I have indeed do a lot of Booleans/Union in this job.

I have tried to separate/rejoin but it doesnt help.

I'll post an other fillet funny behavior I had with my headphone object, where doing a fillet on a selected edge explode the fillet from an other part :o)
(I'll post it asap, have to finish a job first :))