Ok, I think we had a happy end here, after changing the cables it happened only one time, after changing some HDMI-CEC functions over Bravia Sync menu on my X390E (I disabled everything aside from the main function of HDMI control). The issue is gone.Thank you for your input Otto, as always 😉
I can't label the port, and I'm thinking too to have a faulty hdmi port, besides of ARC functionality.
I already contacted the sony support to receive an "official" reply to the issue. Fortunately TV still in warranty.
I'm using KabelDirekt certified premium cables, with the sticker on the package.