De Dietrich MCR3 24T - Pressure drop in a gas boiler installation

Welcome.

I have a house (ground floor and first floor) bought from a developer with a De Dietrich MCR3 24T boiler and central heating installation (horror) without manifolds, no floor. Made on TECE pipes and joints, all flooded in the floor. The installer claims that the pressure test has been carried out. The whole was filled and launched on 19/12/2016, i.e. a month ago. The installation was (apparently) deaerated after commissioning, since then I vented the radiators on the floor 2 more times and were air-vented quite seriously (the air from the raw water from the water supply apparently is still "coming out").
After the last venting, I decided to follow the pressure in the installation and noticed that from Saturday to today (3 days) the pressure dropped by 0.1 bar. Of course, I wasn't venting at the time. I don't see any leaks, but I can't see them under the floor on the ground floor.
The question is: do such pressure drops mean leakage or can they be associated with a constant precipitation of air from "fresh" water?
edit: I was still able to talk to the installation contractor, he claims that 3 days is too short observation time and the pressure may fluctuate (as long as it doesn't fall non-stop ...)

This artist is ........
I have the same boiler and the pressure is constant, of course at the same temperature.
Buddy, doesn't the safety valve drip when heating?

The valve does not drip or from any visible place
A pressure test was carried out, during which the pressure dropped by 0.05 bar within 1 hour, which the plumber considered successful (because the installation cools down, pex pipes can give up a little, his test equipment may have passed something, etc.). The test was carried out at a pressure of 5.5 bar and the installer claims that at such a pressure leak would give a 100% clear pressure drop. At the time of the test, the radiators were cut off on the valves, so their possible leaks could not be detected.
Meanwhile, I heard by ear that one of the radiators makes strange sounds, like "popping". I closed access to it and after one day the pressure in the installation did not change, after another minimal decrease again. Maybe this time the correct fluctuation (about 0.03 bar), I will observe it until the end of the week. If it flies steadily, it's practically back to the starting point.

As for the mcr 3, you have to add a second manomert, the factory will get stuck, all stutter without unlocking, the weakest furnace element usually stutters indicating some pressure even if it is without water and the pump falls. The pressure should be maintained from 1.3 to 1.8 bar and this is normal with the oven running.

For now, my pressure gauge is working - we'll see how long. Indeed, this is a valuable remark, because within X years I could gladly look at constant pressure when in practice the installation is already empty
Returning to my case, cutting off the suspect heater stopped the pressure drop. The leak was malignant, because a droplet appears every few minutes and does not fall to the floor, because it evaporates earlier from a hot radiator.
Thanks and best regards.