Troubleshooting black screen on Oneplus 5T after fall

My Oneplus 5T fell on the floor a couple of weeks ago. Immediately after the fall the screen went completely black. Switching the screen on and off a couple of times it then showed vertical green lines on a white background, going back to black shortly after. My first thought, since the screen looked fine from the outside, was a loose connection between the screen and the motherboard. Today I managed to open it and check the connections. At first they seemed to be loose, but once I disconnected and re-connected the screen-to-motherboard connectors (both of them) and powered the phone on, nothing had changed. Another thing I noticed is that the two connectors are only the two ends of an extension ribbon cable, meaning that there is no physical cable separation between screen and digitizer signal from screen to motherboard. The digitizer still works (as does everything else in the phone that I could check), meaning that a full cable failure is unlikely, right? At this point my only option seems to be a screen replacement, but these things aren’t cheap and don’t always ship where I live (Italy), so before I order and wait for one or find a repair shop that can change it for me, I want to be pretty sure that the problem is the screen assembly. Has any of you ever experienced or repaired similar damage?