Chosen Solution

This iPhone SE, after reconnecting the 3 touchscreen ribbon cables (digitizer wasn’t working) now has vertical lines on the screen and when pressing on the top left corner (parallel with the cables) the screen flickers. I have reconnected the cables twice now and nothing has changed. Is there anything I can do or do I need a screen replacement?

Probably you have to replace the entire LCD module. The best way to know is puttting a new one to be sure. Buy a new one and test it. Worst case scenario you keep the LCD for the future or sell on Facebook Market Place.