22 April 2020
I actually spent quite a bit of time researchung this a few years back, users are reporting the same or similar problems with Thunderolt external drives, USB external drives, and even as far back as firewire external drives.
For any given solution that worked, many other commenters will say that it did not work for them.
Some say that after trying a lot of stuff, it was fixed, but they don't know what exactly it was that fixed it.
Some threads go back for years, and some commenter will say something like, updating to Mountain Lion fixed it, then the next year or so a comment by the same user says that it's back after upgrading to Mohave.
It's a complicated issue and I really wish there was some single solution that would fix everything, but that does not appear to be the case.