Doesn't sound like congestion. In my experience, when entrances are too small the bees land on top of each other and "fight" their way into the hole. Bees can be knocked to the ground in the chaos, the backup spreads onto the hive sides and landing board. You are not describing that multi-layer pile-up.
Hovering flights around the entrance are orientation flights -- and these sometime occur in brief periods (mid-afternoon in my hives). In the buildup period, enormous clutches of brood hatch virtually simultaneously. Does anyone know if the transition from nurse>forager caste is the time of the orientation flight, or if the newly hatched nurse does a flight before assuming tending duties.
Robbing bees will "hunt" back and forth looking for the moment to make their dash towards the opening. There are almost always guard bees at the entrance, greeting the arrivals by touching attenna or chasing the unauthorized off. Do you see that. I almost never see stinging fights at the entrance, but do see the bouncer's chasing off the riff-raff, the guards don't fly by run in patrol patterns on the landing board.
Drone will buzz the hive. I believe these might be orientation flights by the house drones, or drifting drones detecting a virgin queen and visiting.