What is the purpose of the bottommost screw holding the IPhone 5 LCD shield plate? While being sold bottom quality LCD replacements for my iPhone 5 and subsequently returning them six times I lost one of the screws that holds the LCD shield plate in place. It's the one closest to the home button on the back of the LCD assembly. 



Since I continue to have issues with the digitizer / touch screen, I wanted to check whether that screw is somehow integral to the touch capabilities of the screen. 

Some issues I'm having:


No input is registered if I put the phone on a surface and only touch the screen, i.e. without grounding myself by touching the metal case or frame. Plugged in earphones or charge cable works as a substitute to allow input. 
A slightly damp finger makes every scrollview jump around like crazy and makes phantom taps on other parts of the screen.
Trying to scroll with one finger often results in zooming instead, i.e. pinch gestures.


The LCDs were delivered without any sponges on the plugs of the wires, unlike the official screen assembly. Not sure if that's relevant at all.
The missing screw from the heat shield in your image shouldn't affect your iPhone 5 in the way you're experiencing. Its only purpose is to keep the heat shield in place, which in turn protects the LCD from excess heat. 

In your case, since the heat shield is still there, the digitiser/LCD shouldn't be affected by any excess heat, nor the possibility of cables moving (as an added bonus, the heat shield does sort of help keep everything in a place).

It's most likely your problems have been low quality replacement digitisers and/or a damaged cable. However, I have personally seen one instance of an iPhone (not an iPhone 5, but that probably doesn't matter) where a cheap 3rd party digitser/LCD replacement only worked properly when the heat shield was removed altogether. 

I've also heard that (but have no personal experience of) some repairers actually removing the heat shield so that their replacement digitsier/LCD screens work properly.

I suppose you could try doing the same as a 'test'.