Yep, happened to my B7 LG OLED after about 10 months. Watched a variety of content. Didn't game often, but the elements that burned in were folders on my bookmarks bar, and parts of my YouTube avatar. All were yellow in colour and burned in as green elements on the screen. Used it as a PC monitor as well as general use, figured I was careful enough to avoid staying on one kind of image for too long...but I was wrong, it seems. Always turned the TV off if I was leaving a room too. It's put me right off OLED, despite the great picture it provides. Back to a normal LCD until Micro LED becomes cheaper, because that hopefully doesn't have that issue. I just can't be arsed babying my TV, or being told that I'm watching too much of a particular kind of content that might cumulatively fuck up the screen at some point in the future after my warranty is up. Luckily for me it happened within the first year, the TV got written off as uneconomical to repair and got a full refund, but it was still a pain in the ass.
OLED phones can suffer cumulative burn in too. For me, the technology is too flaky. I really do miss the picture quality, but it's not worth putting up with a display that's prone to that shit.
Fingers crossed for Micro LED, but no doubt there'll be some other pain in the ass issue with that too.