It can be a frustrating nonsense at times. I had a flight in F from LHR-ORD cancelled on me just over two weeks out last month. I’d been protected on an earlier flight but left on the original connection from MAN which was just a bit too tight for my liking - plus I wanted a bit of time in the CCR. When I rang the GGL line I was told there was no availability on any earlier flight from MAN in any class that day which didn’t sound likely. EF suggested there was plenty and a dummy booking for MAN-LHR also produced availability on all flights in both classes. So after HUCA I suggested there might be an IT problem which they agreed with but it still took 24 hours for them to sort it and even then they forgot to ticket the first leg - though I had the reservation. I chased that up and got it resolved a day later but it was a bit of pain all round.