Faint horizontal lines on iPhone 6

[iMore Question]

Hi,

I just successfully replaced the front camera on my iPhone 6, however, my screen now has faint horizontal lines, and sometimes thicker vertical lines appear changing in colour. I had this problem before when I replaced the screen on this phone but i can't remember how I fixed it.

I reset the phone, restored from a backup, reconnected all the connectors - none of this worked.

Any ideas?