Red vertical line on a led Acer pc monitor

I've got this old lcd Acer x193w monitor in a home PC building. It's 
connected to my PC by a VGA cable and by an IEC cable to my UPS to be 
supplied.
Today an 1 pixel wide red vertical line appeared on the right side of 
this monitor in correspondence of its on/off button as soon as I 
switched it on in; actually I've been pressing this button quite often 
along the years of usage, if it could be important.

This line doesn't appears in screenshot images but appears in BIOS 
environment and in both one of my OSs and it appears even if its VGA 
cable is disconnected from my PC so I think this issue doesn't deal with 
my PC components; anyway this is my cfg:
- amd ryzen 2200g with Vega 8;
- msi b450-a pro (bios V10.7; 2019-03-07);
- 2x4gb hyperx predator @3200 cl16 (working @2400 by default)
- wd black 1tb hdd;
- corsair cx450 PSU;
- no graphic card.

Honestly I don't know if this is a monitor electronic issue for sure or 
I've to consider other ways/things before trying to fix it, anyway I'd 
like to listen to your opinions.

What do you think the problem is and how to fix it (if possible)?