Video signal loss (solved but I can't explain how)

[DMD]

Yesterday my Q10 Pro started giving me signal loss problems with the TV (OFW 2.1.7) connected to an OLED 4K TV.
The TV was in muting (absence of a signal) in particular when he went to play, I tried to change the display settings and I noticed that the problem did not manifest itself if the box was set to 1080p @ 60Hz.
When reset the correct frequency of the display 2160p @ 60Hz the box stopped the signal with the display for a few dozen seconds and then reappear with the setting at 1080p @ 60Hz.
Then I decided to reinstall the FW without result, and not even making a downgrade 2.1.4>2.04>2.0.3>2.01, even if I tried to set the color space 4.2.0@10bit the screen went to muting every 5 seconds.
I decided to carry out a total restore following the instructions of the thread
https://www.futeko.com/newforum/index.php?topic=1622.msg14469#msg14469
Short-circuiting the two pins appeared the Himedia logo but not the logo to Android and restarted with the last installed FW (2.0.1), I tried two times even with the underlying pins.
In the end I reconnecting it to the 4K TV and checking if the 2160p settings were kept, or updated the FW (2.0.3>2.0.4>2.1.7) I no longer noticed any problems.
I don't know how to explain how restored despite that a real recovery of the box has not been there.