The problem I have found with S5, is that after extraction and re-seat of the lcd, the IC on the LCD digitizer will short. The only way to fix this is to reflow the IC. Not sure if its a plan to fail part of the S5, or just a defect. Lots of customers have reported the "snow" effect occurring on their S5 LCD without ever having a screen replaced, so my thoughts are that they have a weakness in manufacturing that allows the solder joints of the smd IC component to be easily disturbed.
Reflow of this part is an extremely difficult process as it requires temps that can damage LCD if the heat is allowed to overflow onto the nearby LCD ribbon area (!Burn Spots!). Recommend that these units are professionally repaired; even with professional glass only replacement this damage is likely to occur, so dont be shocked if it happens to yours. Almost all units that come in with sturdy cases, such as otterbox tend to not have this issue, so its my opinion that the underlying damage to IC is pre-existing and most likely drop/shock related. Extraction only exacerbates the problem and forces it to become visible.