plugging SSD into different USB ports (buttom right->top left) seems to solve this problem.
Ding! Ding! Ding! We have a winner! This is the known problem with that onboard hub on the Potatoes. The top left port is the “OTG” port, which comes directly from the SOC, and it doesn’t suffer from the weird resetting (?) issues that plague the hub hardware or driver.
What draws my attention in this thread is that it seems that there was a software change somewhere back there that causes, or at least triggers, this problem.