If you get the dreaded 3 beep flood detection alarm, and you keep clearing the water from the flood tray, then there is a real problem.
In my case was also getting intermittent 1 beep error code, that indicates not enough water. This could happen mid wash cycle or on fill. Water level was in fact very high.
On fill this could take a long time, and you could hear multiple fill cycles, resulting in an overflow and the flood tray filling.
The water level pressure switch was not activating properly, switch seemed OK when tested.
Replacing switch made no difference.
Cause is a blocked or partly blocked with gunge hose between the sump and pressure switch.
If you look at this hose and it appears discoloured at the sump end, then this is the problem.
Remove the hose at sump and and clean out. I used a long nylon cable tie, and warm water to flush with a large syringe.
Probing the sump to hose joint is also wise to remove any extra gunge.
This is a poor design, and dishwasher cleaner would appear not to get near this pressure pipe.
So manual cleaning, when you get a 3 beep error code and or a 1 beep code.
Fixed it for me, but the fault will return due to design.