Most likely cause for new display being half dead?
After having had an issue with the original digitizer I replaced both digitizer and display - eventhough my original display had still worked perfectly (i had not succeeded to separate the digitizer from the display). I handled the new parts very carefully without applying any force to these parts. I just glued them together using double sided adhesive tape (which I applied on all 4 sides).
Unfortunately the repair only was a partial success: The digitizer now works but the new display seems to be defective: The bottom 1/3 is OK but in the top 2/3 section every odd line seems to be dead (i.e. this section looks greyish.. also it shows colored vertical bars in it).
I wonder if I just bought I defective replacement display or if I maybe I broke some other phone part during my repair work...
(By now I managed to remove the old digitizer from the old display - by heating it in the stove and then pealing off the disintegrating digitizer. I then reconnected the old display for comparison - eventhough I actually expect that I broke the old display by the rough handling... actually the old display now also shows a similar pattern - HOWEVER the defective area here has a different size, i.e. it is even bigger...to me this looks like an indication that the problem is actually display specific - and not just some main board component which I might have broken.. otherwise both displays should show the same defective area, right?)