There are only two satellite tuners in the 922 (as in other Duo receivers). If one is recording, the other can be used to watch another channel. However, putting the receiver in Duo mode assigns one tuner to TV1 and the other to TV2 so you only get to watch OR record one program on each half of the receiver.
There are other conflicts:
Sling playout places the receiver in Duo mode and takes over the TV2 side of the box.
As satnewb says, if the record preference is set to TV2, then you can't watch anything on TV2 while a recording is in progress even of TV1 isn't in use. At least I think that's correct -- haven't actually tried it.
I believe Sling playout also interrupts a recording! I could be wrong about this but it seems like I lost part of a recording about the time I was showing the Sling streaming to someone.