Seat Allocation goes missing to Las Vegas

I checked my upcoming bookings for seat changes this morning, and then called the FC in a grump.
1) My Las Vegas flight on the 5th October did have a seat upstairs selected for the outbound and return, now it is showing nothing available upstairs on the way out. The FC have made a note in my booking asking for an Aisle seat. The only seats available are middle seats of the downstairs set of 4.
2) My SFO flight on the 22nd does not have the option of selecting a seat, saying they will be allocaqted at checkin. The FC advised that the plane is pretty empty (although as it's half term and I've never seen a SFO flight less than 90% full I am not convinced)
My question is this, is it common to get bumped off the top deck to Vegas ?
Anything I can do to fix this issue ?
Mark
1) My Las Vegas flight on the 5th October did have a seat upstairs selected for the outbound and return, now it is showing nothing available upstairs on the way out. The FC have made a note in my booking asking for an Aisle seat. The only seats available are middle seats of the downstairs set of 4.
2) My SFO flight on the 22nd does not have the option of selecting a seat, saying they will be allocaqted at checkin. The FC advised that the plane is pretty empty (although as it's half term and I've never seen a SFO flight less than 90% full I am not convinced)
My question is this, is it common to get bumped off the top deck to Vegas ?
Anything I can do to fix this issue ?
Mark