Kodi on my Nvidia Shield plays Blu-ray ISOs but won't play DVD ISOs



I am kind of new to the Shield and Android TV.  I have been ripping my media collection of DVDs and Blu-rays, mostly as MKVs, to my Synology NAS.  After trying several playback options, I settled on Kodi and found that the user experience for multi-episode TV shows is better with an ISO rip of the disk.  My issue is that Blu-ray ISOs play just fine, but the few DVD ISOs that I have ripped don’t play at all. I get a Playback failed message saying “One or more items failed to play. Check the log for more information about this message.”  However, the log is empty.  I am using AnyDVD HD to rip the ISOs (yes, I know I will need to find an alternative at some point). On my PC, I can mount the DVD ISOs and play them with PowerDVD, and I can also play them from my NAS with both the Windows and Mac versions of Kodi. It seems these DVD ISOs are fine, but I am stumped as to by the Shield version won’t play them. It is the latest from the Google Play store.

Any suggestions?

Thanks!