Thermostatic valve connection issue

[0Duke0]

Hi, the other day I had a plumber over to fit a new TRV to a radiator on the ground floor. During the process I noticed the pipe connecting the valve to the piping under the floorboards was not properly clamped and was turning first counter and then clockwise. When the valve was fitted the pipe had settled half turn clockwise from its previous position. I asked whether that would disturb the seals to the T-connector under the floor and the plumber assured me it shouldn't be a problem. In the days since I've noticed a 0.5 drop in the boiler pressure over a week. Could the leak be caused by the rotating pipe? Any ideas before I have the plumber come out, lift the carpet and the floor boards and investigate?
Many thanks

 

[oz-plumber]

Depends on what type of fitting is under the floorboards.
Some fittings allow the pipe to rotate while holding a seal.

What sort of pipe is coming through the floor, if copper, what sort of pipe do you think is under the floor.

If it's 0.5 bar over a week, it may be due to draining down to replace the valve and the system getting rid of air or expansion tank settling.

I wouldn't take the floorboards up at this stage.
Monitor the system for a couple more weeks