When you setup a scroller on a fixture and assign it a dmx address, it does not indicate in the list of dmx addresses that a scroller has been assigned to this address. Everything works okay, but it just looks like the dmx address is unassigned when trying to assign dmx addresses to other fixtures.

Ross

Yes, this true.
Scroller is passive 3D function and should be patched over any active DMX dimmer in the system that will catch the signal.