I have had similar problems with OS engines so i'm wondering if your new engine was an os. I fly mostly smaller engines though.
If you search the problem of peeling liners in RCU all threads point to os which has been having an ongoing problem with this. I actually like the brand but am tired of changing the piston and liner every season. Even though they stand behind the product I just don't think it's necessary to have to do that. I have started to sell my OS's and replace them with other brands.
So to ask, is your engine is question an OS?