Chosen Solution
My friends MacBook Pro 15" 2014 shows some pretty weird behavior. When booting up the process suddenly stops and and a black bar appears on the upper part of the screen. Then nothing happens anymore. I tried to find out if it was a graphics problem and connected it to a screen over the Thunderbolt port. It booted up normally and i can even disconnect the screen and work normally. It even works when i only have the VGA-Thunderbolt adapter connected without the screen. (For DVI and HDMI the cable/adapter isn’t enough, there needs to be a screen attached, guess that’s a digital/analog thing) He had NVIDIA CUDA installed and i removed all that because apparently that isn’t supported in Mojave anyway. This didn’t change anything though. Does anyone know what might be going on here? Thanks!
Carefully examine the display for any impact anomalies. It can even be the size of a pinprick. Does it look kind of like this?
To be on the safe side first do a PRAM reset and an SMC reset. If this doesn’t work are you able to boot into network recovery on the internal display? This will rule out a software issue. See this guide on booting into network recovery: https://support.apple.com/en-gb/HT204904
