no allowed rooms when using tags preferred rooms

[giameg]

Hi, I have some teachers to be available for substitutions. I want FET to choose this activity. Since I have three buildings and constraint min 1 hour gap between bld chng, I setup the following parameters:
-created subject Disp
-created three tags disp1, disp2, disp3 to be linked to the 3 buildings
-created activities for the teachers with disp, no groups, 1 or more tags because some teacher are available in more than one building
-created 9 rooms and linked to the building (3 rooms for each building) because I want to have max 3 teachers available at the same time
-set up the constraint space->tags->activity tags has a set of preferred rooms (tag disp1 - room1,room2,room3) (tag disp2 - room3, room4, room5)...

when I generate the simulation is impossible because I get the error as in the picture

[giameg]

UPDATE I found out that the problem comes from activities with more than one tag.
I don't know if it's a bug or it is simply not possible to allow multiple tags for an activity
By the way, I solved splitting in more subactivites and assigning to them a single tag, and it's now simulating

[Volker Dirr]

The way you descriped your problem and solution looks ok.
FET support multible tags. That shouldn't be the problem. (Of course it will care about ALL tags that you add). I done it very similar (but just with one buildung).
Maybe attach your (simplified) example file to check your problem.