Kind of watermark on background video Philips monitor

[MrNice]

I just want to tell that I found the issue is due to the monitor
hardware; When I disconnect it there is a small moving white window.
Looking at it thoroughly, I can barely see the stripes.
I can't believe that but I have to, I never saw this kind of failure. I
can't say if it is the panel or the video electronic. As this device is
9 years old, I'll open it to check connectors and solders (when I have
time).

Sorry for the trouble