Sadly, the issue remains.
Steps I did:
Downloaded new DMG.
Dragged new program to Applications (chose to keep both in case of any problems).
Opened new program. Clicked yes to "this was downloaded from the internet are you sure" question.
Opened folder of photos. Resumed going through them. (By the way, would it be possible to have a "jump to last modified file" keyboard shortcut within the thumbnail view to get to the last file I rated or saved?)
Clicked the green circle of the preview window to go full screen and pressed f to get rid of all panels then double clicked to reopen both side panels while still keeping top and bottom panels gone.
Rated a few photos, then got to one that needs to be cropped and saved in a couple of different aspect ratios.
Dragged the first crop area.
Command + S.
File saved.
Uh oh. As soon as the file save happens, I'm exited out of the full screen preview "space" and bumped back to the thumbnail sheet.
Previously I turned off the options suggested to make PM6 go faster and so I'm not any longer in the right location the thumbnail sheet (but very close because I've only gone through a handful of photos). However, as I discovered from a lot of web searching I can get back to the preview "space" by using an Control + Arrow (first attempt didn't work because I tried the wrong arrow direction, and then the other Command + Arrow key worked; macOS seems to be pretty random about whether the preview space is a left arrow or a right arrow to get back to). As I mentioned, I can get back to the preview space in just about 5 seconds total from the time I'm kicked out of it, although I have to wait for everything to save and stop processing the shift out of the space and back to the thumbnail sheet. Then if I wait long enough for 2-3 seconds I can do the Control + Arrow and get back to the preview space and a second later I can start working again. But as I said even if this is just five seconds of delay, it slows me down a lot over the course of a day (perhaps a minute of time or so wasted for every five minute of work).
Other notes and observations after this point:
"Photo Mechanic 6 2" which is what the Finder decided to name the new version. So I checked the dock to make sure I'm really using the new version you provided. Yes, I am using the new version.
Also checking "About" from within the application. It says Photo Mechanic Version 6.0, build 3286 (1728a38).