Try disabling Edge on startup and reboot. I know, it doesn't sound like it would be related but this fixed it for me, and I can't explain it. problem is, after a windows update, it was back on in startup, so I had to disable it again after that.
I started Taskmanager and killed alle Edge and webview process. I was able to copy more than a GB of data. Excatly at the moment I opened Edge, my USB disk dropped out, and copying halted..