I've heard people say they've really mangled up those brakes when they aren't securely hooked into the hammer spring. The mag. catches the bottom edge and pushes/bends the brake and the only way it can bend it forwards in the mag. well and then you can't insert the magazine till you get the ruined brake out of the frame.
Yeah, my Pre B CZ85 no longer has the mag. brake in it. Don't remember if I threw the mangled up brake into the garbage or a scrap metal box.
Have you noticed the P07 and P09 pistols don't have the brakes at all? The hammer spring is exposed along the back of the frame/mag. well and doesn't seem to be an issue on the P07/P09 pistols.
Most folks in the US aren't into magazine brakes anyway, it's a European thing I think.