ERR opens actuator although it is too warm

Hello everyone and please don’t hit me.
Actually, the ERRs have been dismantled in all rooms except the children's room.
The thermostat is an RTR from Halmburger, with a display from 0-6.
According to the manual, the temperature should be 20°C at level 4, but in the room it is now 22° and the actuator is open and the room is being heated. When I set the room thermostat to level 3, you hear a click and the actuator closes, but shortly afterwards the actuator opens again, even though the room temperature is still around 22°C and the RTR is set to level 3.

Shouldn't the RTR only open the actuator again when the temperature in the room falls below I think 16°C at setting 3 on the RTR?

Or am I making a conceptual error here? The temperature is measured directly next to the RTR.

Shouldn't the RTR de-energize the actuator when the room temperature reaches a certain value? I understand that these analog RTRs are not the most accurate, but 6-7°C inaccuracy?

Draft present?
How "cold" is the wall where the thermostat is hanging (is it an exterior wall)?

No, it is not an exterior wall. I would have to measure the temperature at the wall, I should get myself a device for measuring. There is no draft either. Window closed, door closed

I cannot help technically but can only say from my own experience that determining the room temperature is not that simple. For example, I bought Zigbee sensors and placed them on the wall thermostats (height 1.4m but directly on the wall). And these measure slightly fewer °C than, for example, a thermostat placed in the room. A curtain in front of the room thermostats can also distort the measurement result.

Such an IR thermometer is quite helpful.

I also have Zigbee Tehomastate from Aquara that stick right next to the RTR on the wall.

The radiator thermostats are actually always bimetallic strips and that says it all. The Aqara devices have an accuracy of ±0.3°C so now it's also so-so.