Brieuc,
for all valves but one the situation has improved dramatically. Thank you for that.
For my bathroom, the valve still does not close fully, I just touched the radiator and it is warm (not full-power but still heating) but no request for heat is needed and displayed in the app:
The radiator has the connecting terminals (hot/cold) at the bottom, thus the valve sits only about 15cm above the floor.
Netatmo station in the same room also measures temperature still quite differently:

- Screenshot-2017-12-7 quellenweg.png (11.28 KiB) Viewed 344 times
I have customer-support case JUV-ZKYFX-016 open for this and granted access.
Let me know if you need anything more (eg. photo of the radiator) to track down the issue.
Thanks,
-Markus