Hello Arno- I tried re downloading and reinstalling both the latest UVI workstation and B-5 v2. Here is what i have found so far.
I am using a novation Impulse 49 with cc# settings that match the default set
of B-5 v2. In the standalone version of b-5 i can control drawbars-percussion
reverb distortion etc. --But when i Move the control assigned to key click-
I get a red box around the gui and the program freezes. This even happens
when i try the midi learn function- as soon as i move the control to learn click
volume- the program freezes.
Now for the interesting part :)- When i use it in mainstage i am able to "Map
a Mainstage controller to the click volume by clicking on the click volume knob in the gui (standard mainstage mapping procedure) I get the red box
and the program freezes but when i reload b-5 everything works as it should.

I only use this in Mainstage so far anyway- so - so far so good.
I am using a 2012 quad 7 mac mini - 16 gig of ram - ssd- latest version of
osx Sierra. Latest version of UVI.
Really love this program- key click is not a deal breaker- but just wanted you
to know what i've found.
I quess if no one else can reproduce this -it must be on my end, but not sure
what else to do.
Thanks in advance