I'm a bit confused on your setup.
Sat Box -> Matrix Switch -> Theater
Sat Box -> Matrix Switch -> (future garage?) (bedroom?)
How does the bedroom tie into this currently so that you can see something which causes a drop?
I've always used Extron matrix switchers (RGBHV/RGBS) with audio to be extremely reliable with very high compatibility and functionality.
Extron Crosspoint Series Switcher 12X4 | eBay
I just don't really understand how things are connected which would cause any issues at all.