If I create a mask that's specific to a surface, it does not show up in the output on the PC version of the software. I was able to replicate the exact same procedure in the Mac version of the software and get the results I'm looking for. Both are the same version. Here's my process:
Place siren generator on surface.
Enable mask on surface.
Draw mask on surface.
The PC version shows it behaving properly in the output preview window (when both input & output are open side by side), but it does not show up in the actual output. I've tried this in both Spout and external output (when connected to a projector) and the result it the generator fills the entire window.
Again, if I replicate this process in the Mac version, everything works fine.