Maybe the do all stress evenly, but my exposure to the problem was dependant on the amount of bowling balls that were being bought in my area. When Zones were all the rage I would've said Brunswick was the worst for cracking. But for a while columbia and track sold huge in my area so I repaired a whole lot more of these. Just in sheer numbers, not percentages, that's what I saw. Sorry for writing it in an such an odd fashion originally!
Right now we are selling a lot of Ebonite, Hammer and Storm equipment out of the shop I currently work in and have not really noticed a whole lot of these issues. Now I'm not sure if this has so much to do with differences in resins utilized now a days or just the fact that there are different drillers in the area then compared to my earlier years?