It has been suggested in the past, since that since switching users seems to fix the problem, that there is must be something in the user account that is amiss (such as login startup items or an old virus detector that was long forgotten and not totally deleted) and perhaps an Apple 'Genius Bar' at an Apple store might be able to locate the issue.
The root cause has never been found because it is impossible to troubleshoot without having possession of the Mac. Every year (going back to at least 2014) there have been a few Mac users where NOTHING other then switching user accounts will allow it to update (or fix other issues).
I did not suggest that work-around because it is so rare, but is not new and had persisted for years. Something in my main (administrator) account is conflicting with TT startup.
The meantime, a workaround is to create a new user account in MacOS and launch the program from there.
