First of all, thank you for developing, maintaining and continuously improving this great tool.
I was able to successfully backup this blue-ray disc using MakeMKV; however, decrypting the contents have been a challenge so far. Both attempting the decrypt it from the disk and from the backup copy consistently gives the error mentioned in the subject line. The disk contains the movie "The Wife" (2018). I am happy to provide more information or insight as needed.
Thanks!