MacBookPro only boots when an external screen is connected
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?