Fills with water slowly when not in use

check water solenoid

If water slowly fills in the tub when not in use.

a) Most likely your machine inlet water valve not seating properly and closing. Change the machine water valve.

b) May be sink drain water back flowing to the tub. But you have checked that.

So it has to be the machine inlet water valve.

Not sure if you mean that it fills all the time and overflows or you mean that it just always fills and never has enough water.
The first problem would refer to a faulty water level switch - need to replace.
The second would be that the washer drains as it fills - if the drain hose is lower than the washer, inspect the anti-siphon valve.

The pressure switch, also called the water level switch, is what control the amount of water goes in the machine, If your machine is constantly filling to the overflow point, then that is your problem. Now, if water is going in and the level is staying the same then your machine drain line is lower than the pump and your siphoning out the water as it goes in. Pull the drain up a little a that should fix the problem.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/jason_4570d45317834dd3

try to keep the drain hose above the height of the washer, as it may be siphoning out

check flapper for proper seating or cracking if water constantly draining into bowl

Try this, unplug washer for two minutes, plug back in, open and close lid seven times slowly, this will reset the computer and the electronic motor. Also on water level switch, make sure hose from switch to tub is not plugged, blow it out, gets clogged with soap.

What is error code?
Does unit spin?
Does unit drain?
Does unit fill on all water settings?
Ie set to hot, warm, and cold and see if fills.

check that the drain hose saises above the water level of the tub. I f the hose does not come above the water level, the water will just drain right out

could be leaking inlet valve or if drain is plkumbed in unbder sink, could be filling thro drain pipe when you emptyt sink