I met two folks here on the forum who had multiple slide stop breaks. Both returned the guns to CZ, and CZ replaced the guns. (Apparently the openings on the frame were slightly out of spec.)
I suspect the problem is the gun, not the stops.
If the slide stop isn't setting perfectlly perpendicular to the barrel, when the slide slams forward, the full impact of the slide will be focused on a smaller are on the stop -- and that will eventually break it.