Fortunately, no. I have 18 USB drives and was very happy when I discovered that DrivePool did not require Drive Letters to work. I have auto update on Windows 10, so I imagine I have the latest updates. Everything is working fine here.
Although I do not use Drive Letter assignments, I have all my pool drives named. Since I am so clever, I named them DP01, DP02, DP03, etc... and they sit on a shelf in that order, too. I also labeled the drives with a small tag. Makes it easy for me to pull a drive if it has any problems.
I hope you find out what happened to your DrivePool and why you now need Drive Letters assigned. I'll be reading to see what develops. Hope you get a fix soon.
Yup. This is an issue we see from time to time, and it's a known issue with Windows (not our software).
Specifically, the issue is that ... sometimes, windows will not mount a volume if it doesn't have a letter (or path) assigned to it.
Fortunately, this is a dead simple fix:
https://wiki.covecube.com/StableBit_DrivePool_F3540
