Still more: I just realized that you've never told us if your problem occurs in a test user account. (It's THE most basic troubleshooting step, and I've completely forgotten about it 'til now, which will give you some idea of how little troubleshooting needs to be done these days.)
OOPS! You did, and I went ahead and totally missed the significance of your problem's not following you to a test user account combined with its following you in a safe boot. It means that something, but neither a login item nor extension, in your user account is corrupted (and that a reinstall won't fix it).
I'm not sure that it'll help, but based on your description of your problem, I think it's come time to rebuild your LaunchServices database...another quick Terminal project.
If you happen to be conversant with the Terminal app and the macOS command prompt, there’s a command that rebuilds the LaunchServices database. Type it (or copy and paste the following) in at the command prompt, press Return, then wait for a few minutes until the command prompt reappears:
/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user
When the command prompt reappears, type:
killall Finder
then press Return to relaunch Finder and begin using the rebuilt LaunchServices database (Emphasis added)
Apps such as OnyX and Cocktail have this functionality built in, so you can also go that route if you've got such an app and it's up to date.
