[Solved] Karcher 5.55 - no water pressure, the engine is running all the time

Hello, I have a similar washer because K5.55m I have a problem as in the subject of low pressure. Additionally, after releasing the trigger, the engine pulses every 2 seconds. I greased all the o-rings, no damage is visible on the pistons or the sealants, I replaced the lances with the gun. Please advise which valves may be the cause of this failure.

Either you can't read or you don't feel like reading everything is described in this topic.

I had a cracked upper cylinder head under the valve. The cost of a new cylinder head was 95 zlotys. Thank you and good luck.

Forgive the excavation, but I didn't want to start a new topic because I have exactly the same problem as the angelic one here. Unfortunately, in my case, cleaning and lubricating the shut-off valve did not help.
The washer works normally when the VarioPower nozzle is set to low to medium pressure, on the rotary nozzle or the rotary brush for cleaning the terrace (although I have the impression that it is a bit uneven, which is best seen on the gun itself or even without a hose - the pressure "floats" slightly). On the other hand, with the VarioPower setting from half to MAX, it turns off regularly every second, although the pressure for this second of operation seems to be correct (removes dried-up worms from the mask).
You cannot see any cracks in the head, the washer was used very sporadically, maybe a dozen or so times from new products, and was always stored in a heated garage, so the frost did not affect it for sure. She also never worked long at one time.

photos: https://imgur.com/a/m2chliK
action videos: https://www.youtube.com/playlist?list=PLRy5wZ6qe5FhfFM-VaC3FxhkYJyM75pV1

EDIT: I add photos and videos

Clean the nozzles

Thanks for the answer.

I understand that the nozzle from VarioPower? It was honestly the first thing that occurred to me after the onset of these symptoms, because you can see that she is a bit stony, I even undressed and cleaned the regulation mechanism, but I thought such a symptom was something more serious. I'll throw the descaler nozzle only for a while and we'll see.