Hi John,
I tried your Ingest on my X.10.11.6 Macs and the card does get unmounted as long as there aren't any errors during the Ingest process. I also tried a card with non-photo files as well as some image files, which did log an Ingest error and the card did not eject, which is normal behavior. When you are done with the Ingest and the card is still mounted, can you go back to the Ingest dialog, select the card and then click the Unmount button? Does this unmount the card? If not, then there is probably another application ( possible the Photos app ) trying to access the card. If the card does unmount from the Ingest dialog, then please send a copy of the PM.log.zip file. This can be accessed from the Reveal Support data option in Photo Mechanic's Help menu.
Thanks for your help with this issue.
--Bob