On my test I have added the line in the beginning of the [Unit] section:
[Unit] Description=Make remote CUPS printers available locally Requires=cups.service After=cups.service avahi-daemon.service Wants=cups.service avahi-daemon.service ...
Perhaps this makes some difference. Perhaps you should also try to remove cups.service from the Wabts= line in addition.
On my test I have added the line in the beginning of the [Unit] section:
[Unit] cups.service service service
Description=Make remote CUPS printers available locally
Requires=
After=cups.service avahi-daemon.
Wants=cups.service avahi-daemon.
...
Perhaps this makes some difference. Perhaps you should also try to remove cups.service from the Wabts= line in addition.