Immergas Zeus 20 Victrix Boiler: Recurring E10 Error after Central Heating Startup

Hello
First of all, I'd like to say hello to all forum users .

I am asking for advice on what may be the cause of the repeated error E10 before I order a service for the boiler.

Description of the problem
The error appeared after starting the central heating..
After resetting the furnace and heating the DHW water, the furnace correctly switched to central heating.
After heating, the entire central heating system in the house was vented.

Symptoms
If the stove, after heating the central heating, stops for a few hours and then switches to central heating, it automatically receives the error E10.
Switching to DHW (the stove heats the tap water) will unlock the E10 error, then the stove will easily switch to central heating.
After the heating is completed, the stove if it stands for a few hours and the CO is turned on first - I get the E10 error again until the DHW turns on.

Additional information,
Pressure regulated at 1.5 b - does not drop.
The system seems to me that it is vented - all receivers are warm.
The boiler is a little over 6 years old.

Thank you in advance for the information
Jarek

Error E10 indicates a problem with the flow of water through the boiler exchanger.

When using a pressure sensor

When it occurs
If the terminals for connecting the pressure sensor to the boiler board are open.

Verification
In the event of a short-circuit of the input on the board, the boiler should start.
If there is no voltage on the protection element from the board (check without the element connected)
this indicates damage to the board.

Cause
1. No water pressure in the boiler circuit.
2. Air in the system.
3. Contamination in the pressure sensor inlet.
4. Sensor failure.
5. Loose or dirty connection at board or sensor terminals.
6. Damage to the wires connecting the sensor with the boiler board.
7. Board failure.


When using a pressure switch or flusostat.

When it occurs

If, when the pump is operating, the terminals for connecting the pressure switch or flusostat to the boiler plate are open.

Verification:

In case of a short-circuit of the input of the pressure switch or flusostat connection to the board, when the pump is operating
the error should disappear. If there is no voltage on the safety element from the board (check without
connected element), it means that the board is damaged.

Cause

1. Lack of water in the boiler circuit.
2. Choked flow through the exchanger:
a) dirty system filter, closed thermostatic valves (with the boiler by-pass closed),
b) contamination of the exchanger from the water side,
c) pump gear set too low,
d) dirty or broken pump impeller,
e) too low pump power - partial short circuit in the motor windings.
3. Pressure switch or flusostat dirty.
4. Damage to the microswitch of the pressure switch or flusostat.
5. Loose or dirty connection at board or microswitch contacts.
6. Damage to the wires connecting the sensor with the boiler board.
7. Board failure.

I guess that's all

Regards

Thank you for the information,
Will try to verify the checklist as far as possible.

Regards