I just have to thank the maker of MakeMKV, version 1.9.9. It is the best version by far to date. I've used it for many different movies without a hitch.
I was having problems with other parts of the process, but no problems whatsoever with MakeMKV. And by upgrading the firmware on my blu ray optical drive, upgrading to the latest BD Rebuilder, and using Verbatim 97457 blanks, now I get perfect back ups every time. I was so used to having one problem after another (especially the dreaded I/O error) on about every 4th Blu ray, but no more.
Thanks so much!