I have encountered this issue many times for a couple of weeks. I encountered it using USB sticks, ArcDisks, and now with my hard drive docking station.
It was working fine when I copying data files from a hard drive in the docking station. Then it crapped out where I had to reboot my system to clear the hung USB mount after typing continue a couple of times.
Most times it doesn’t cause a hard failure…it just can read only. Move the same USB stick to a different operating system…no issues.
Any ideas how to fix this?