www.makemkv.com

Ive had a few movies out of every 30 or so end up with flaws. One skipped the last 5 min of a movie and oddly jumped to the anti pirate screen. Another locked up after 5 min of playing and you cant skip the chapter. Is there a self check function to validate the backup? These are both disk backups. Both 4k. Or its just playback and hoping it works. I try to keep them finger print clean but some seem really sensitive.

Also some movies keep asking the language in the beginning. Is this normal? Is there a way to set once?

MakeMKV does a "hash check" of the files when doing the backup, and will generate error messages if the checks fail.

What you describe is probably Cinavia copy protection, which normally would only show up if you're using a "Certified Blu-Ray player" for the playback.