Yeah its thats last " just one more cut to clean up" that will get you. I have had that happen more than once and I guess I needed to learn the lesson over and over to get what not to do. I know better than to go back to the thin areas after getting into a vessel deep but I still have done it and sometimes with very light cutting I have gotton away with it and others times it has cracked. I knew better but still tried to do it......now I just reach in with 60-80 if the opening is big enough and sand my way.
If you have a scrapping cutter on, freshly sharpened, and a very very light touch to the exact area - you could get away with it (maybe) but, if any of those things are not right the risk increases way up........I think by now I have learned.......I think........LMAO...................
Frustrating to think of how long you spend to get it to the point you do and have things go wrong....but I spend time when I cool down to analyze what happened and to think thru how I can prevent it again in the future....