Very interesting. Thanks for your comments above.
Same as you, I ran the invasive analysis software and looked over the reports, and then realised that I could censor/redact the confidential bits before sending the reports to the Malwarebytes forum, but then I decided NOT to send the reports anyway as I could see that - with or without the confidential bits - the reports clearly gave no useful information that would help in problem analysis/resolution. So Malwarebytes were just jerking the users around.
Also, same as you, I went back (last time was a while ago though) to see if there were any developments on the problem resolution. There was zilch.
Oddly enough, I did actually play around with my RAM disc in temp, wondering whether that might be the causal problem - because it had been a known (avoidable) problem in the scripts that install/start up Google Drive. However, I still couldn't get the MBAM installer to work. Tried again last week.
Hmm...odd. If it worked for you though, then it should work for me (OTBE), so I may have made a mistake somewhere. Shall re-check today.