You shouldn't need a tester to see burn in though, either the images is burned in or not
also it could've just been image retention, the LG CX, C1, and all the ones after that Have pixel refresh so you don't get that, the older models suffered from it
plus i have five years burn in coverage from the best buy insurance plan, so I use it with no fukks given, I didn't spend 1500 to have to baby and barely use something, I haven't had any problem yet, but I keep my desktop a black screen with the icons hidden, so when the desktop is resting its all black and the TV isn't using any energy
But you do need it.. And it is burned in. Image retention goes away. The LG C8 has pixel refresh and all the technology you're talking about in the cx.. They out here feeding people lies to purchase the tv