No audio from speaker when jack connected to rear TB16

Another issue with Precision 5530 + docking TB16 (what a nightmare of purchase!!)

Suddenly, after a month of use, audio of speaker stop working if the jack is connected in the rear plug of TB16 docking (I have two of them, office & home and both don't work, so not a hardware problem)

If I connect the jack to the PC or to the front plug of TB16 and change the input on Sound control Panel, it works.

Btw: every time I plug the jack I correctly indicate speaker as inserted device

Reinstalled Audio Driver of Realtek (7-aug) for TB16, nothing changes