[Discuss] Video interference from MATE desktop environment

[epp at null.net]

I was logged in with the MATE desktop and after I opened an Incognito window in Chromium - thus displaying a (mostly) black window, I noticed waves in the display, as if there were some sort of electrical interference affecting the monitor. The analog video cable running from the PC to the monitor has one of those magnets built into the cable.

I eventually logged out of MATE and logged in with LXQt. When I checked the Incognito window in Chromium under LXQt, the waves in the display were gone.

The video chip (onboard) is: Advanced Micro Devices, Inc. [AMD/ATI] RS780L [Radeon 3000]

The monitor is a Sceptre X9g Naga III (19").

Could something in MATE - or that loaded in with it, could have caused the video interference?