sounds like carp to me. How long did this engine run before you found this problem. I think most will agree there is very little you can do to cause a ring to break like that. If it only ran for a short time I'd be willing to bet they were broken on assembly.If it ran for a long time the rings would be in short little pieces and it would be pretty hard to determine if they were "in spec" or not. I'd be real leery about this shop, you might be better off cutting your losses and taking it somewhere else IMO.