Do you remux to MKV? If so, does it succeed for both good and bad copies of an M2TS? My experience has been that MKVToolnix will hang on a corrupted M2TS (because it has to actually parse out the data, instead of just copying bytes), and thus have been simply remuxing directly from disc to avoid copying the data multiple times, relying on the remux failing to detect problems. Of the movies I’ve watched completely since, I have not seen any macro-blocking that would be indicative of only a small part of the stream getting corrupted. It seems highly unlikely that random corruption would hit only the HEVC stream, and not any of the TS headers that encapsulates it. Also, like I said, the corruption problems, when they occur, are repetitive for me - the per-block decryption key is wrong. The problem your describing is almost as if your drive is returning different data each time it reads. Which shouldn’t be a thing - all optical discs after audio CDs include error correcting codes so that you’ll know when you read something wrong, and often times can correct it. Audio CDs didn’t have that, and thus AccurateRip was born as a database for people to know if they ripped tracks correctly, similar to your requests for MD5s of the main title TS.
(Btw, my drive is a WH16NS40 SVC50 - the one that doesn’t officially support UHD and AACS 2.0, and I can’t use to play encrypted discs in PowerDVD, but works with DeUHD, and once decrypted, PowerDVD will play discs just fine).