Hello every body can someone help?

One wheel is slightly leaking ( 0.2 bar per week) while the other do not leak at all.

The car is equipped with the Tyre Pressure Monitoring System. The default occurred after a valve cap has been removed for pressure check. Before it was not leaking at all.

I would like to avoid to remove the tyre.

Can some one post pictures of the TPMS and especially the inner part of the valve where it is in contact with the rim? is there any Gasket? or is it metal to metal contact?

I am thinking of re-tightning the valve from external. Is this a good solution?
Any other idea without removing the tyre would be highly appreciated?
Thanks in advance

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Present cars:
My car: E-class 420CDI, 2008, W211, V8, 180 000km

Wife's one: C-class 220CDI Sport Coupé, Euro, 2002, W203. 345 000km

Son's one: GLK class 220CDI, 2009, W204

Sold E class 260E, W124, 1988 beloved car sold after 489 000 kilometres of reliable services (engine M103, clutch and 5 speed manual gear box all original).

E-class, W210 320CDI, 2000[/B], 225 000km, Sold