Moving hazy rectangular bars on Samsung LED TV

This bug on my moms TV started appearing a few months ago. While digging through all posts regarding defects like this, with most resulting in the diagnosis "Display needs to be repaired, defective pixels, internal hardware failure etc", I found one post where a commenter suggested turning on a 4K video on youtube. Despite not believing it would do anything to fix the TV, I told my mom it doesnt hurt to try. Completely absurd and unbelievable, but she told me that it indeed fixed it. For the past few weeks the problem reocurred sporadically, and the hack always helped. Now I saw it the first time myself and I just cant understand what is happening. So I am posting here and maybe someone has enough technical knowledge to explain the phenomenon...