Just a little post to celebrate the end of the bug !
As I already told you, I suck at understanding what's going on inside a computer, so I'll probably suck at explaining how the bug died. I'll try
After deleting and reinstalling different version of my graphic card drivers (a very old one, an old ones and the last one) without any changes, I decided to just delete the drivers and to reboot...
I was expecting something like a 800x600 display with 8 colors, but it seems like everything was fine, my desktop was looking good, I tried the viewer... And the bug is gone.
I wanted to be sure so I tried every softwares I could to check if there was no other problem.
AND THERE ISN'T ANY !!
Even if I had a plan B, this bug was stuck in my head, forcing me to think about it when all I needed was ideas and focus for the concert video.
Let's pop a new screenshot to celebrate this !!