Are there any official responses here on how to fix things?
What I eventually did here was move the entire library from one external drive to another one (larger) in one large copy, so there should be no fragmentation of files (if that matters) and reinstalled 18.0.8. This seems to make it play OK
Since this will be running headless, I tried Gizmo on my android tablet. Making a connection isn't much of a problem, but as soon as I do something on the tablet, MC crashes. I click Relaunch and have to go to Options, Media (whatever it's called) and do the entire process to generate the passcode each time. No idea if this is "normal" or if it should start by itself, but once I pick up the tablet, it crashes again. Sometimes I get a message that the server can't be started.