Yeah it's happened to me a number of times so I book row 3 instead to insure extra space. Problem is when it happened last two times it was a same day sub out. Or at least they didn't inform me in any way on the app. I checked about 3 hours before the flight and it all appeared fine and then got on the plane and the exit row was 3 rows away. I explained it to the FA and she said it was a pretty quiet flight so go ahead and switch but that was lucky. The flight before I lost it I checked maybe a week before and didn't see any issues so I assumed it was ok. Went through the seat selection on check in and it still seemed ok. Got on the plane and it was not and it was a full flight. Not too happy about it but that's flying for you.