I have at least 4 DPMS Ambi safety's and they have all been broken at one time or the other.  Some of  them extrude further from the lower more than others and are easily broken when carried on snowmobile, atv etc. I don't know if this is a tolerance problem with DPMS or the lower or a combination of both.
The JP kit is only slightly higher than the DPMS but both are overpriced.  For an extra charge you can also buy an additional selector arm and make the JP ambi.  With very limited use I have had no problems with the JP breaking and consider the left/ambi safety a bonus to an outstanding drop in trigger.