Hi !
Indeed, the issue happened right after I got the device back. Actually, the motherboard was dead, but they changed it for free since it was still under warranty, they updated the Bios, reinstalled the OS and everything they needed to do, including wiping out my SSD, but hey, that's standard procedure...
And yes, the picture was the absolute exact same as mine.
However, I managed to solve the problem, the culprit was Windows Update Manager (WuMgr) it's useful to block annoying Windows Updates, but it also blocked some driver updates which apparently were required, it works fine now.
One of this driver was the good one, I'm not sure which, but it's not a hard guess.
Screenpad 2.0 update caused a LOT of different problems to a lot of people, it got a lot of hate, also in this forum, for very understandable reasons, and Extension display is one of them.
2.0 does indeed have an Extension Display feature but it is the worst thing I have ever seen, I can't get into specifics, but there are topics all over the internet about this.
It's very different from 1.0, which basically just works as as second screen, that you can use simultaneously as trackpad, while playing a video on it at full brightness, for instance.
That just became impossible with 2.0, you could use your screenpad as a second screen while using it as a trackpad BUT you had to manually switch to "Touch mode" which basically turned your screenpad display to 15% brightness, making it unusable to watch videos or do anything with both screens at the same time, effectively killing the "Screen Extender" feature.
They probably did that to focus on these dumb "apps /toolbar" for which there are not any SDK available.
Anyway, there are dozens of posts that explained it better than I did, but you get the idea... I'm glad I paid to downgrade to 1.0 which was just fine.
Thanks again !