Some degree of DSE is normal for LCD TVs, and you’ll see more of it on FALD sets (which are also much more common than they once were). Very poor uniformity/bad DSE may warrant a return/exchange but TBH I’m not all that bothered by it.
Can you lie a TV flat?
You aren’t going to damage the internal workings of your flat screen TV by laying it flat. … That being said, even though laying your TV down flat won’t cause internal damage, it could be a recipe for external damage. There’s a complex balancing act going on in the way that flat screen TVs are constructed.
How bad is DSE?
DSE is awful. Only really noticeable on bright solid-color areas during panning/scrolling scenes, but once you see it, you can never unsee it and it will drive you crazy forever.