Life made simple so I don’t have to drag you through a lot of posts/reading.

Shorter barrel means higher residual barrel pressure of the spent case to the chamber wall during unlock.

The brake is adding more pressure (back pressure) down the gas port (making the gas port act as if it was sized larger), hence making the bolt unlock even faster (even higher residual pressure over just the shorter barrel alone causing the case to adhere to the chamber walls even greater).

This boils down to the spent case just being more tension bound to the chamber walls during unlock, with the B/C losing too much momentum on the rearward stroke pulling the spent case out of the chamber, and the end result being buffer impact to the back of the receiver extension being less than stellar.

Bottom line is the mag is not getting the items needed (normal end of stroke impact jarring/rearward stall time) to allow the mag to recover before the bolt moves back forward to cleanly strip a correctly seated round.

For the solution to the problem (read if you don’t want to just remove the brake), there are more than a few ways to correct it, but read these posts for a solution that will best suited for your needs.

Read this for a primer,
www.ar15.com/forums/topic.html?b=3&f=66&t=266108

Then read this,
www.ar15.com/forums/topic.html?b=3&f=14&t=153425