Makemkv successfully creates .iso, but can't save titles from it

[dxrmkvun]

I have successfully created mkv files from numerous discs, but I have found a TV series DVD set that makemkv (ver 1.17.2) has a problem with. Using the Backup function, Makemkv successfully creates .iso files from the discs. I can play those files, with no errors, using VLC. So the .iso files are good. However, makemkv is unable to create .mkv files from the titles in the .iso files that it created (or, for that matter, from the discs themselves). All I get is the following error, with no explanation:

Using direct disc access mode
Calculated BUP offset for VTS #0 does not match one in IFO header.
Title #1 was added (20 cell(s), 2:23:56)
Operation successfully completed
Saving 1 titles into directory C:/Zappiti
Failed to save title 0 to file C:/Zappiti/A1_t00.mkv
0 titles saved, 1 failed

Can anyone provide a solution for this issue?

[wmcclain]

Have you tried the different DVD opening modes as detailed here? viewtopic.php?f=7&t=28541

Or, you might note the title numbers when playing with vlc and use manual opening mode in makemkv.