I was going to say magazines, but you've tried more than one. I'm having a hard time believing a brake could cause these malfunctions, but as that's the only thing you've changed I'd recommend taking the brake off and head back to the range with the bare muzzle to see if the problems go away.

The only other thing I can think to try would be a different weight buffer, maybe a heavier one to slow the action down? That's assuming it is cycling too fast. But the brass ejecting at roughly 90 degrees seems to indicate it's not cycling too fast, doesn't it?

__________________
- Fourth Horseman -