We had a Bramley once on limiting root stock and it mostly grew suckers.....so it got taken out. Is it still establishing itself....say under 4 years planted? Maybe a good trickle watering overnight near to the trunk might help. Take off some of the smaller fruit if can be safely reached. Try not to let it set so many fruits. Remove at white bud stage if reachable, and some more after the June drop. I have grown apples in the garden for forty odd years.....they can be a bit cussed...pests....messy grease banding....poor sets....to big a set.....frosts...sudden leaf losses...no fruit at all.

it could be just the shear size of the apples to . maybe when you take some of the fruit of take of the bigger ones .

Maybe you could use some of your big dropped apples as 'exploded apples'. Wash and do a wide core a use a micowaveable bowl. Chop up the soft parts of the core and place the apple on top. Fill the centre with blackberries. Sweeten to taste with chosen sweetener. You can use raisins too as not all have berries. Cover the bowl with cling film or plate or saucer. Microwave in short bursts of 45 secs as at some point the apple will 'explode' and puff up somewhat. Custard or cream to help it down.....delicious.

cant you make some apple pie with them come to think of it ?