Sometimes but not every time when washing, error 20 ⇐ Electrolux

[Andrey air]

Dishwashers Electrolux ESL 47710 R
The machine is about five years old. During long programs, sometimes but not regularly it shows the 20th error approximately in the middle of the wash, after turning it off and on it brings it almost to the end, but again SOMETIMES but NOT ALWAYS (including on a 30-minute short program) the 20th one pops up error. Sometimes the entire wash goes through without any problems. The technician (called when error 20 started to appear) did not “identify” the problem, he said that everything was fine (I was not standing directly next to him. During the first visit, he said that there was a leak from under the lamp - he fixed it. After his second visit, everything was still the same - 2nd drain error). At the end of the wash there was no water in the car, I checked the filter. I would be grateful for advice: what is the possible problem, is it possible to carry out simple repairs on your own (you are handy yourself), and if a specialist is needed for replacement or is required, then where to find him in Moscow so that everything works without problems after the technician leaves.
With respect to everyone and requesting advice on the merits and not commenting on my / master’s actions

[Guest]

Addition. I checked the supply to the pressure switch and the water drainage. Everything is clean, not clogged. As an “amateur” in this topic, I blame the pressure switch, especially since the car gave the 40th error a couple of times - and this is regarding the level of the water sensor. On the other hand, the car works and happens, albeit rarely, without problems. Tell me - maybe the problem is in the pressure switch. The master, who came a couple of times, said that they rarely fail.

[Guest]

Addition. Finally got lucky with the master. When defecating, after inspecting and checking the tubes, I assumed, based on my own experience, that the problem might be in the pump; if the floating error remained after replacement, then the next step was to reflash it. Moreover, in case the error persists and a flashing is required, money was not supposed to be taken for the pump. Replaced the pump. There really was a big gap in what was filmed. For several days now everything has been working on all programs. Maybe someone will find this information useful.
I wish everyone good equipment

[Guest]

I’ll insert my 5 kopecks. PMM Zanussi is the same nonsense, it either leaks or doesn’t. I took everything apart cleanly. The drain pump hums but is quiet and does not drain. I checked it and connected it to the network without water spinning. The drain is located 10cm above the pump, apparently it cannot pump.