The fact that when you sent in your first UpdraftPlus support request we were all a decade younger (and UpdraftPlus was just me and a free plugin; updraftplus.com wasn’t even registered until a week or two later) blows my mind. Glory to God. Glad you’re still here!
You can see in the code – https://plugins.trac.projectdmc.org/browser/updraftplus/tags/1.23.3/class-updraftplus.php#L2078 – that UD calls the WP function to know what the uploads directory is. So apparently for some reason in your install, that returns a wrong result. Do you have an over-ride set in Settings -> Media, or via a constant, that you need to update after moving your site?
No overrides. Media items would all be broken if they were pointed to a missing directory. I guess it probably isn’t worth the time for either of us to try to figure this out. Switched to BackupBuddy.