So Adobe today released Beta’s of apps in the Creative Cloud app that anyone can download, and so I decided to test the Alexa test footage and my own footage, and all of it works fine. So this was certainly a bug and it is fixed in the Beta.
I would love to be able to check the release notes to see what they fixed, but I haven’t figured out if there are release notes for these public betas.
EDIT:
OK was still having some weirdness when I opened up a project that is working fine in 2020. I was still getting the weirdness when trying to play back the sequences, but if I reload the footage it then works fine, and this did not work in 2020. WTF!
Oh well it actually works now, so no complaints.