Discoloration corner on monitor

[cmjb13]

Hope someone can assist...

I have a 1991 WWF wrestlefest cabinet.
Original monitor WG25K7193

I swap boards often and I noticed the top left corner of the screen is discolored.
I played around with the left speaker and noticed that when I moved it, the colors changed

I removed the speaker completely and the discoloration is still there.

This cabinet does move from time to time (to swap pcbs)

I'm a newbie when it comes to monitors, but what I'm reading is that a degauss may be in order.

Any advice is appreciated.

[Slippyblade]

That's a de-gaussing issue.  If the monitor has a de-gauss circuit, use it.  Otherwise you might need to pick up a tool for doing it.