I'll see if I've got anything to help you when I get into the office tomorrow.
A non return flap doesn't keep the water in the machine, it stops dirty water being sucked back in, hence the reason I said to keep the drain hose higher than the machine.
Unplug the appliance, pull it out and take the rear cover off.
Open the filter door and take the filter out.
Take the plastic panel below the front panel off.
Undo the screws holding the filter housing.
From the rear, take the pump and filter housing out, disconnect the wiring and the hoses from the pump.
Check the hoses for any debris.
Now the pump is out, check it for this item that keeps blocking it, remove it and refit the hoses and wiring to the pump.
Refit the pump and filter housing, refit the panel and the filter.
Try the machine out.
If I find any diagrams, they will be exploded parts views, they don't always help but I'll post them tomorrow once I get in the office if I have them.
Hope this helps