Topic: switch dock problem: working on 1 of 2 screens (hdmi)

hi there,

I'm having a weird issue with my dock for the switch:
I have 2 "monitors" to play (but use 1 at a time, not dual screen), a TV samsung QE55Q6F and a computer monitor (benq xl2720z).

I usualy play on the tv, but when my wife is watching something i don't like ( ) i play on the Benq screen. It worked for a few month ( i bought the switch a few month ago). I had no problem. When she would stop watching (or falling asleep ) i would get the switch back on the tv. Everything worked fine.

My samsung tv that usually detect what i plug in (telling me that it's IS a switch, a ps4, etc, with a proper icone, etc and would change source once i plug the console in the dock and turn it on).
A few days ago, a weird bug happened; the tv does not recognise the console ( it's now unknow, no more switch icone and doesnt change source once the console is plugged) BUT... i can play, except for that, everything is fine ( video and sounds are there).

Then, my wife was watching something the other day and decided to play on the Benq but it didn't worked: i get a no signal. Impossible to play on the Benq but still ok on the tv (except the unkown and icone thing)

tldr: my dock is working on my tv but not anymore on my computer screen.

Some more informations for those who may help:

-tried several hdmi cable (and tested them, they work with other devices)
-tried other hdmi port
-dock and charger are official
-tried the plug in order ( unplugg everything, then power, then hdmi on dock, then hdmi on screen, then console on the dock, then power on the screen) and it didn't work
-tried another dock (same problem)

Any one has an idea or suggestion on what it could be?

Thanks

ps: English is not my native language, i hope i ddn't make too much mistake and that you can understand everything ;D

Set switch settings to 720p.