iTunes deletes/removes podcast episodes it should not
I have a podcast set in iTunes on my Mac to NOT delete played episodes, and also set on the Apple Podcasts app on my iPhone to NOT delete played episodes. Yet when I play an episode of that podcast with the Apple Podcasts app on my iPhone and then sync my iPhone with iTunes on my Mac, the episode disappears from iTunes on my Mac. This should not happen.
Possibly related 2nd bug: When the associated mp3 file of the "disappeared" episode is not deleted from the podcast's folder inside the iTunes Media folder (which used to happen occasionally but now appears not to happen any more for this particular podcast, i.e. the file seems to always stay around), I try to put the episode back into iTunes via the "Add to Library..." command. I can see the mp3 and Add it (via the misnamed "Open" button) but it does not then appear in iTunes, i.e. there is no way to make the episode which iTunes erroneously removed visible again in iTunes.
I have seen some descriptions on non-Apple sites of how to rebuild the iTunes library, and I'm willing to try it if that might help, but I'd first like to see an Apple-authored description of how to do it properly.
AdThanksVance, Rico
Mac mini, macOS High Sierra (10.13.3)