Weird grey lines on starting screen, in system blue lines.

Hi there!

I would suggest the following:

1. Disconnect/remove the display.
2. Inspect the display ribbon cables for any pinches or tears and inspect the connections and contacts on the logic board for any damaged pins.
3. Use a Q-tip dipped in Isopropyl/Rubbing Alcohol to clear out any debris in the connections and contacts.
4. Re-secure the display connections and reseat the display.
5. With the new screen installed, power off the device and let it sit untouched for at least 6 hours.

If this doesn’t help, it is possible that some sort of damage did happen during the repair or pins on the connections on the display or it could simply be a bad display. Hope you are able to figure it out though!