Grey sceen with lines when starting up (macbook pro 2011)

[AnatolAl]

I‘ve been doing some light work on my trusty macbook 13“ (ssd, ram, thermal paste, battery) and so far it has been running well, except when i take it on the road. It‘s always a bit scary and i‘ve been trying to avoid it but as soon as is start up there were some vertical lines nicely distributed on the screen, no apple logo - just a grey screen. Normally it went away after a couple minutes or when i started it up again but now its stuck there. The evenly distributed lines still show up at the start up but change to a centre bulk of lines with different colors after some time. When i press against the back of the screen there are some reactions, thats why i figured it would be the connection cable between display and motherboard. Can anyone tell me if i’m right and is this is still fixable?