I'd also contact Horizon or the place you bought the engine. I haven't heard of this happening before, but it's possible. Were you running the engine on the lean side? Could it have been running hot? I'm not at all saying it's your fault, I'm just curious.

Btw, you're not the only person to have to over-ride the stops on the Evo engines. Needle settings can vary quite a bit depending on fuel and air density and humidity. So the problem there might just be that the place where it was run is different enough from where you are.

(btw, before you rush off to OS, you might want to know that the OS FX line of engines had a major problem with exactly the defect you just experieneced, the liner would peal off if the engine was run too hot. They seem to have corrected the problem, and they are good engines, but they aren't immune to problems either)