This cleared up all the other problems I was having with Premiere 2019 (13). I'm sure Adobe will delete this post if I were to link directly to the instructions on how to do this, but if a cat were to walk across your keyboard and accidentally type "Premiere Project Downgrader" into Google you would be pleasantly surprised.
I don't think this is a general solution, even if it seems to have temporarily worked for you (though I'm glad to know it did).
Reason is, this problem has been going on for years, pre-dating 2018. Adobe refuses to do anything about it, inviting us to leave Premiere for less buggy apps (e.g., DaVinci which incidentally costs much, much less).