Hey Matthias, I'm experience kind of the same behavior in my UCX (USB v1.72, TMFX v0.983 RC2). Let me elaborate on this a little bit, got two workspaces:
#1: Mains assigned to phones 7/8 set to -?, all other outputs set to 0db
#2: Mains assigned to outs 5/6 set to -?, speaker B assigned to phones 7/8 (linked to mains), all other outputs set to 0db
to me it seems like as you pointed out, "all ! routings and gains have to be reset and reloaded", so, a quick but "scary" reset to 0db it's happening.
Two questions, first you pointed out that "This is a technical limitation..." of the UC and F400, but is this true also for the UCX?, and second, if it is software related, why not reset the gains to -? instead of 0db?, it makes more sense to me.
Thanks in advance MC.