Add a height selector and use it as a mask for something. Change the height selector parameters. The only way to get it to update is to restart WM (using pro 2.1, 64bit).
This bug is present with any mask input, and is already fixed in the upcoming v2.2 
Awesome! I don’t suppose I could get a build could I? I had to restart WM every 2 minutes last night just so the output was right 
No, but you shouldn’t have to wait more than a week before the patch to be released.
Before that, you can reproduce the mask behaviour with a Chooser.
Imagine you wanted to connect device A to device B, and to use device C on the mask input of B :
A—B
C__|
Instead, connect A to the input #1 of the chooser, B to #2, and C to #3 :
A—|----------|
B—| chooser|
C—|_______|
The chooser output will be the same than the output of your previous device B
(Sorry for the ugly ASCII-explanation!)
Excellent - thanks for the workaround