The "return to XM 1" paid me a visit twice today. This morning when I was listening to ogg's on USB (side note, thanks GM for offering this capability as I'm one of the 10 people in the world who will probably use it.) I flipped over to XM and it was back on XM 1, changed it to something else, parked the car. When I came back out to the car after work, started it up and it's back on XM 1.
Sometimes upon startup it reverts to a previously played XM (non-1) channel. I haven't noticed anything odd with XM if I don't have a flash drive connected -- not sure if it's that's a cause or if it's just coincidence.
A couple of times it also has forgot what directory I'm trying to play on USB and will revert to the same directory that was being played a few ignition cycles ago.
10.29-95283115 sw version on mine. It needs to go in for the update anyway, hoping that it helps...