Smart Toilet bi-stable solenoid valve acting strange -what could be the reason and the fix?

Question

I have a smart toilet (Ove Stan) that is built using this valve Here is the valve manufacturer page but I can't say exactly which one of those is my valve.

It is acting strange as described below.

I called the toilet manufacturer and they want me to replace the entire assembly.
Here are the directions they sent me

Here is how the toilet works: when I flush the toilet there are two valves that open in sequence:
The left one in the above picture is what they call the whirlpool valve which is cleaning the toilet bowl before flushing it.
It basically sends water to make sure that all goes to the bottom of the toilet.
After that this valve closes and a second one situated at the bottom of the toilet opens and it flushes/pushes everything into the drain.

The problem: the whirlpool valve is not working anymore - not as it used to. In normal conditions it won't open at all anymore.
However by accident I discovered that if I open the sink tap half way that decreases the water pressure in the pipe that supplies both the toilet and the sink and then if I flush the toilet while the water is running everything works relatively normally. Obviously there is a lower pressure at the bottom valve in the toilet but it is still enough to push everything into the drain.

I am not sure if the valve is broken or if it is that the water pressure is too high and I should try to lower it at the toilet supply end.
That end is controlled by a SharkBite 1/2 x 1/2 Inch MIP Straight Stop Valve, Quarter Turn, Push to Connect Brass Plumbing Fitting but I can definitely put something else there.

I do not trust the manufacturer who is telling me to buy the entire assembly and to replace it.
That generates more profit for them and it seems like a waste to me. Besides that it will be difficult to access the back side of the toilet to remove the assembly, I would practically need to remove the toilet because it is installed too close to the wall.
Based on the valve manufacturer pictures it should be easier to replace just the valve from above.
If based on what you see in the picture (Model F62B08BOL) you know of an equivalent please let me know.
The water pressure measured at an outside water tap is shown below. That is located just before the pipe enters that bathroom.
It shows around 90PSI, the valve is rated for 0.8Mpa (116PSI).

Here are the toilet details, I can't find the pressure requirements: https://www.ovedecors.com/en/plumbing/smart-toilets/stan-toilet.html

Here is the plumbing recommended by the manufactured for this toilet:

Update: of course I am actively researching the topic and I am thinking, could a pressure reducing valve be installed after that tap you see in the plumbing diagram?

Answer 1

So the problem here seems to be the pressure not the valve. I suspected that if I buy the entire assembly again it would also end up ruined because of the existing pressure issue

The solution was to use a pressure reducing valve that I could install just behind the toilet

Here you can find the details, what components and where to buy them
https://terrylove.com/forums/index.php?threads/smart-toilet-bi-stable-solenoid-valve-acting-strange-what-could-be-the-reason-and-the-fix.107155/post-763449

Answer 2

$1,000 toilets. What the...

You did some great diagnostics, which I believe answers the question - just not the way you want it to:

It shows around 90PSI, the valve is rated for 0.8Mpa (116PSI).

Which means the water pressure is within the nominal range of the valve. Which means the valve is not working as designed. Which means replacing the valve/solenoid assembly is the right thing to do. Yes, the entire assembly. It appears to be two solenoids/valves and a base plate. Yes, that costs more. I doubt the manufacturer is making much money on it, because small parts orders are a pain for manufacturers.

There are things that could go wrong if you try to replace just one solenoid/valve - e.g., the plastic plate may not really be designed to handle replacement. The manufacturer may also be concerned that if one solenoid fails then the other one may be likely to fail soon as well.