I just wanted to post a solution I found and a thanks to Dangelus for the help in my previous post. I didn’t realize I did not actually have debug logging turned on.
Once turned on I discovered the problem that was causing Kodi to take forever to play random movies and sit at “Working… Please Wait”.
I had most of my movie library in one folder, many of them in rar format (for par2 bitrot protection). There were about 3500 rar files in the main folder.
Kodi was doing this:
22:31:34 T:6152 DEBUG: CUtil::ScanArchiveForAssociatedItems:
Searching every last rar file for subtitles, via Wifi and a USB HDD.
The reason the issue was so random was subtitles were turned off on some movies and not others, and it would sometimes be temporarily fixed after a reboot likely due not properly closing SMB connections.
I moved each movie into its own subfolder and now all movies play instantly.
I had always assumed Kodi would search only archives with the same name when searching for subtitles.
PS: Thanks for pointing out I had banned addons. I had long since forgotten about a tryst with crappy TV addons a couple of years ago… they are gone now, but they weren’t the source of the problem as I tested that first.