Fill fault on top tub and bottom works fine. getting about 30 ounces of water and it takes about 3 minutes for fault code to come up

My machine limped along for a few weeks with an intermittent drain fault and then threw in code F51 occasionally. The F51 code is a water inlet fault, suggesting that water isn't filling the drum to the correct level. Clearly the first thing you need to do with these faults is check the obvious.

Drain fault:
Is the drain hose and drain filter clear?
Does the pump sound like it's running?
Is water actually being emptied?
F51:
Is inlet water pressure ok?
Is the inlet water filter clear?
Is water actually filling the drum?

In my case there was no suggestion of an obvious fault. So what makes the machine think there's a problem with water entering AND leaving the drum? It's the water level pressure sensor. The sensor itself is at the top of the machine, but a pipe connects it (via a small plastic chamber) to the very bottom of the tub. Water entering the tub rises in the pipe, thereby altering the pressure of trapped air and telling the machine when to stop filling or draining.
After dismantling the machine and removing the big hose connecting the bottom of the tub to the pump the sensor pipe is visible through the hose hole, which is quite large. So this pipe is in a good spot for collecting gunge and if it gets blocked it's a problem. Clean it out with an old toothbrush or whatever, while trying not to push it further up the pipe.
You should get some compensation for this effort when you empty the coins out of the hose you removed!
So I said 'after dismantling the machine' like it was child's play. It is pretty easy actually.

Open the door. Disconnect power.
Start with the lid. Two screws at rear, one each side under screw covers. Grip lid at front and lift up. It can be a bit stuck so give it a tug.
Remove powder draw.
Lift control panel away from front panel and lay on top of machine. You don't need to disconnect anything. Now you'll see the top of the sensor pipe.
Remove drain filter to empty any water in the bottom hose.
Remove - two screws at the top of the front panel, two screws either side of the door lock, one screw just below the door.
Lift the front panel off of the retaining pegs and pull away as far as the door seal will allow. Pulling away the top of the sensor pipe gives a bit more movement.
Now you can either remove the door seal and take off the front panel, or do as I did, which is just move it slightly to the side, giving access to the screws of the left hand side panel. Remove all screws for the left panel and it's easy to get off.
Now you have good access to the pump and bottom hose. The bottom hose has two clips on the tub end, but only the top clip needs loosening to remove from the tub.
Remember to mop up any water from the bottom tray when finished or you'll get a flood fault.