Chosen Solution
Just out of nowhere my system has on the internal display some weird strips. But works fine with external monitor. Screenshoots are taken show no strips. If I move the screen a little downwards the stripes are gone and display is good, backlight is working. PRAM & SMC reset didnt change anything. Might be just a loose cable somewhere? How to fix it? It was for repair half a year ago cause a broken touchbar. But now its out of warranty. As the next repair shops is 2 hours drive from me I would love to find another solution.
Just another case of kinked display cable, replace the entire top clamshell.
