Update, we figured out what's going on.
If you have a Berserker and you have Paddle Switches, the tac switches underneath the paddle switches could cause the circuit board to be "pushed up" and mess up the mic jack alignment. The solution is to ship the Berserker back to the shop, where they will open it up, uninstall the tac switches, re-drill the holes about 0.75cm closer stance, re-install the tac switches, and all will be well and fixed.
The "old" location for the tac switches for paddle switches pushed against components on the Microsoft circuit board. We could plug in the jack fine at the shop but by the time the package is jostled around by the post man and arrives at your location the circuit board has worked it's way up, blocking the mic. This was baffling for us for a couple of weeks as we were specifically testing every controller by inserting the mic jack and everything was fine, but customers were receiving and saying the mic jack was screwed up.
After a lot of investigation and testing this is the issue, the issue specifically affects you if you have Berserker plus paddle switch, and the solution requires redrilling and reinstalling the tacs about 0.75cm in a different location, this moves the tac switches to a clear space inside the controller and more more interference or pressure on the Microsoft circuit board. Sorry for the slowness in figuring this one out. We thought we found the issue several other times and were wrong each time.