www.makemkv.com

Also to note: both new 4Ks were Disney discs, TSOM and Rocky Horror.

I've also noticed this across multiple new 4K discs. New Blu-Rays are fine. My drive has been cross-flashed for over two years, just cleaned, discs are spotless and were cleaned with micro-fiber cloth when failing. Perhaps this is a new software bug?

UPDATE: Had to rename the KEYDB file and relaunch a few times but MakeMKV now decrypts the disc

Still getting a volume key unknown error with the new KEYDB

Submitted dump for the 1967 How the Grinch Stole Christmas