Issues with mounted disk images

[HarryLime]

In the old days (10.4.10) and SD! 2.1(?), I had a scheduled job to smart update my users folder to a disk image on a NAS. It was not overly quick, but it worked fine.

Since updating to 10.5.2 and SD 2.5!, the first smart update works fine, but subsequent ones fail.

most recently with this error:
| 09:33:03 PM | Info | ......COMMAND => Verifying that mguserbackup ACL support matches al_book_hd
| 09:33:03 PM | Info | error (22) from /Volumes/xxxxxbackup. (Invalid argument)
| 09:33:03 PM | Error | ****FAILED****: result=5632 errno=0 (Unknown error: 0)

Another symptom is the volume containing the backup image can not be unmounted, supposedly in use (it's not). After a restart everything seemed to work fine. I wonder whether a sleep cycle in between may be to blame??

So basically, the routine that used to work fine is somehow broken now.

Thanks in advance..
MG