I don’t have a Mac, but there was recently a mention in a 2.0.5.108 topic of build issue of unsigned builds, which was going to be looked at. I’m not sure if 2.0.5.107 has the issue, but I suppose you could test 107.
Beta should want version 10. 2.0.5.106_canary_2020-05-11 went to 11. There’s no 12 that I could see here.
Do you recall how you did that? Download from releases and manual install should overwrite Beta version.
Downgrading / reverting to a lower version talks about where updates are stored if autoupdater does them.
You can look in the upgrades folder to see if it has upgrades from the web UI autoupdater. If it’s there, then the question would be why it wasn’t picked up. The main Duplicati install should find and run latest update.