Continuous disk not ejected properly message
I have a Samsung 1TB SSD USB drive. It's been on the system for a good few years now. I upgraded to Mojave, and now it isn't seen, or is seen temporarily, and I repeatedly get the "disk not ejected properly" message.
I've checked the connections, tried it in various sockets, but I'm reading this is happening to a few Mojave users. Is there a fix? Or do I go back to High Sierra? If so - How?
Mojave 10.14.4
iMac 27", macOS 10.14