Underfloor heating leaking? Is moisture rising up the wall?

slowly it is forming on all 4 walls in front of the utility room.

But only 2 walls are marked in the drawing!?
Where is the HKV located?
Have you already checked the heat pump/underfloor heating for pressure loss? If it comes from the underfloor heating, the pressure is "in the basement."
If it comes from a water pipe —> meter method (as already mentioned).