I too have an LCD bruising concern when pressing on the front glass towards the top of the unit. I disassembled and cleaned all parts twice for quality control. During reassembly I paid close attention to the concern area. Still noticing some slight bruising on the LCD after reassembly.
During my initial teardown I noticed that the individual I purchased the damaged iPhone from had been nosing around the guts, ergo: missing and loose screws etc. I also noticed that this person tried prying the front display and bezel away from the midframe using what ever they could find -- most likely a small screw driver.
- It's possible the previous owner slightly warped the midframe assembly during their attempt to separate the front display and bezel from the midframe.
Conclusion: in my particular case the LCD bruising is being caused by air gaps between the front display bezel and the midframe -- because the gap tolerance is almost infinitesimal and there is no visible obstructions preventing the front display bezel from seating flush to the midframe -- adhesive will most likely correct the concern
For everyone else experiencing an LCD bruising concern.
- Always prior to reassembly clean and inspect your parts.
- As stated above make sure there is no debris stuck or gummed up where the front display bezel and midframe meet.
- Use Rubbing alcohol 70% "it's in your medicine cabinet" and a foam Q-tip -- not cotton to clean and degrease with.
Side Note: In the iPhone 4 repair guide it calls out using Windex to clean and degrease wi-fi antenna components and other parts, . . . don't use Windex because there are additives that could leave behind a potential film or residue in certain ares. Rubbing alcohol evaporates on contact and is all one needs to clean and/or sterilize conductivity "metal to metal" components.