Screen unresponsive after battery replacement.

After replacing my battery yesterday, the screen worked fine for 1–2 hours. Then the touch functionality stopped working in the top third of the screen. Within 30 minutes, there was no touch functionality except for the bottom 5 mm of the screen. I left it overnight, and now the screen flashed a few colors and won't turn on. I assume the phone is on since it vibrates when I hold the power button. After opening it up again, I checked the connectors for display, battery, buttons and coil, which were correctly seated. The display is still black.

Is the only option a replacement screen, or is there something else I can try before committing to that option (200€).

EDIT:
For some reason, the screen now flashes on dimly and the shuts off quickly while a white line appears in the top third of the screen when I press the lock button.

EDIT 2:
After turning off and on again, the display turned on for a split second showing the boot process, but faded to black right away. I can make out a faint Outline of the google logo afterwards, but nothing after. I'm starting to suspect that the backlight isn't working...