Immergas Combi Oven: Frequent Cleaning Needed Due to Green-White Precipitate on Heat Exchanger

Hello all,
I have a problem with the Immergas combi oven, which is two years old and I am looking for advice. The furnace was assembled by the installer, and had acceptance after assembly.
Every six months the oven needs cleaning. A green-white precipitate regularly forms on the heat exchanger (it seems to be the correct name). The effect is always the same, i.e. the first symptoms of this phenomenon are ash particles appearing under the furnace. Then, but only after the evening baths, i.e. when the stove works with increased power (heating alone does not cause such effects), the carbon monoxide sensor begins to activate. After a few more days, in the same circumstances, the stench of flue gas begins to feel, and after a few more days, the stove begins not to heat up the domestic water.
After removing it, you can find a lot of ash inside, which I believe burns on the burners and hence the smell of exhaust gases and activation of the carbon monoxide sensor. It is necessary to clean the heat exchanger, which is clogged with this ash and sediment, which probably causes reduced heating efficiency, and after cleaning it is calm for half a year, after which the situation repeats for the fourth time ...
Can anyone give you a hint what could be the reason for this?
I would add that earlier in the same place and the same installation was installed an old gas furnace, still with a "candle", which was several years old and there were no such problems.
Thank you in advance for your help.

Do you have propane or network gas? see what is written on the nameplate, what kind of gas, what type of furnace with closed or open chamber, give the model where it is installed, is there a mechanical air extraction in the room, is there an air intake and a ventilation grille?

And at what temperature does CO work? (which one do you have?)

I apologize for the delay caused by my trip. I am already answering the questions:
- the furnace model is NIKE STAR 24 3 E,
- the furnace is connected to the network installation and is intended for natural gas supply,
- open combustion chamber,
- the furnace is installed in a utility room with an area of about 18 sq m, a ventilation hole (gravitational ventilation) is located in the ceiling about 1 m from the furnace, there is an air intake directly under the furnace,
- set temperature: utility water 45 degrees C, heating 55 degrees C.

From the description, it looks ok and there is nothing to fault, maybe not enough air from the intake, or a stuck chimney, a bird is sitting, since the type of gas is ok, only the local vision of the brave technician stays. what does yellow flame and high tongues look like or low and blue ones?

To tell the truth, I don't see a flame. Even if I remove the casing, you can only look inside the nozzle chamber through a small hole. The flame is blue, but its height is difficult for me to say.
The chimney is unobstructed, I checked and cleaned the cleaner. As for the amount of air from the intake, I have no doubt about that - I feel a clear inflow of air all the time. The service technician during the last visit even said that it can be closed down a bit, because it only cools us down the room and generally the layout and location of the room according to him does not cause the risk of too low air supply. Anyway, I clean the stove for the fourth time, for the first year the intake was open for full and the same effect. Then for the second year the intake was open to the minimum and the effect was the same - cleaning the oven every six months.

You checked if the chimney has a draft and how big it is.

The chimney had a review made by a chimney sweep shortly before assembling the stove, which I now have a problem with. In addition to cleaning, the string was to be checked. I was not in person, but the result was positive. I assume that since the chimney is now unobstructed (checked), the sensor starts to turn on (and you feel the fumes) as the stove is extremely dirty (once every six months), and before that for several years an old gas stove was connected to it and it was ok, I think it has the required parameters. Nothing around the chimney was changed or changed.

What surface does the boiler heat? Type of installation, what radiators?

The furnace heats an area of 100 sq m. All radiators are panel mounted. I do not know how to determine the type of installation ... possibly a hint.

Insert a photo of this ash.

This is how it looks.
After removing the housing, the inside is full of ash such as at the pump. In addition, the heat exchanger is covered with greenish-white coating, which is as if peeling and burning on burners. Generally, in the final "phase", the gaps between the fins of the exchanger are full of such ash / muck and the heating efficiency decreases significantly. As normal, without changing the parameters on the stove, I heat the water to a temperature at which it is already brewing me, so it is at most very warm. After cleaning, i.e. after pushing through these gaps, everything returns to normal - for half a year .

Straighten the fins of the exchanger, because now the exhaust gases have a difficult flow. The second thing is not enough combustion air, as evidenced by these black particles. The burner (mixing chamber) must be perfectly clean and adjust the parameters at max and min power.

I always try to straighten the slats after cleaning.
Since I am not a professional, I will pass your comments to some smarter installer, because parameter adjustment seems to be a task for someone who knows about it. The whole story is that the furnace is not my property (rented premises) and the owner's trusted installer says everything is ok . I live well with the owner, so I wanted to gather some information and arguments to discuss myself to convince him that, however, I think everything is not right, because he does not have even the slightest insight into such topics.

I apologize for reheating the topic, but in my case these green and white particles came from an aluminum spiro tube. This pipe is not intended for gas furnaces, because it strongly corrodes, but I currently have one. So it can happen that the particles formed in this way from the spiro tube fall onto the exchanger or nozzles. Every half a year I vacuum the nozzles and the exchanger, because there were explosive ignition caused by the nozzles being strewn around the spark gap