You need this:
http://aminet.net/package/disk/misc/PFS3_53 (what is mentioned in PFS3aio readme). There you will find docs and needed tools. With SetDeldir you can set or deactivate DelDir. E.g.: "setdeldir dh2: 0" to deactivate the DelDir on dh2:.
DOpus5 commands have (sometimes) options that you can check. Check also different attributes. In environment prefs there are settings for delete for example. Go through all and read the docs. There exists some hidden options you can check. Oh... I would also try directory cache settings.