Script Unmount APFS volume

I have used this script "forever":

--DAILY  UNMOUNT 

do shell script "diskutil unmount 8867CB16-4539-165B-A1AC-2DCF6D697LRC"

I have safe booted, first aided the drive, switched ports on this 2019 iMac The drive works fine, it's just the unmounting script that is a problem. The same unmounting problem happens with 2 other APSF volumes on the same drive, each in their own container.

When using the same script (using mount instead of unmount), there are no issues. FYI, I am just mounting and unmounting the drive, not opening it at all

Since Monterey, it either times out, sometimes works but takes a while to unmount, or most of the time I get:

Thanks for the help