on OS 12.3 I have the following problem with a Canoscan 9000F scanner.
(it worked on previous versions of OS)

when I call scanimage from the command line, scanning works fine.
(eg. "scanimage -d pixma:04A91908 -l 30 -t 50 -x 80 -y 80 --resolution=75 --mode=COLOR --format=pnm > tmpn.pnm")

however, when the same scanimage call is issued form a perl server program, that is running in the background, the scanner only makes a short sound and scanimage hangs with the massage that the device is busy.
the scanner then needs a resoff to be accessible again.

strangely, very very rarely the scanimage call form the background is successful!?
but never for two consecutive calls.
from time to time the scanimage call from the command line shows the same blocking behaviour.

does anyone have an idea what could be the problem and how it could be solved?