I think there's another bug in 3D View.
I've done as you described (all done in Demo Show V8)
I've select HTP Mode and took "moving_light_spot_#1" and assigned Pan & Tilt.Midi to DMX fixtures channels
in tab Fixtures, click on button "Menu" in the toolbar in tab Fixtures, and select "Fixtures Midi inputs"
press "learn" and move the midi slider/button (then you see the midi infos at the left side of the "learn" button)
select the priority mode with the dropbox
add an optional comment
press the button "Add / Update"
select the line in the list
check the channels to drive with the midi input
Checked it in DMX_Bragraph. Both channels are blue marked.
Moved the assigned Midi Sliders -> Bargraph moving and a real connected Fixture too.
Gone to "Live" switched on 3D View Button and opened the 3D View Window.
But in 3D View I can't see the fixture moving!
Then I switched on a Spot light color scene and now I can see fixture moving.
Switched it off -> no moving. Switched on a Led Wall Scene -> I can see moving
To result is: I doesn't matter which Scene is switched on, only if a scene is on you can see the Head moving in 3D.
Hope you understand?