iMac 2015 Image Retention after 20 seconds...

After upgrading to Big Sur I now have image retention (can still see desktop icons, top bar and dock). Running the screen saver for a few minutes causes it to go away. However after just 20 seconds the image retention is there again. I stopped the screen saver and no image retention there. I counted to 20 and opened safari full screen... can plainly see the desktop icons, top bar and dock... should this be happening to a display that's only 5 years old? I have several IPS displays that i have had for 10+ years and none of them suffer from image retention. This is my first display to ever exhibit this problem. After searching the web I see that this seems to be a problem with 2014 & 2015 imacs with the retina display. Is this just a flaw with the panels?