Wow after deciding not to bother with iPad Mini's some 8 months ago after suffering many of the above mentioned effects I decided to have another crack this week..........4 replacement digitisers later!!!!!!! I might have cracked it. I cannot express how high my blood pressure must have been during this repair. Every time the touch screen was going mad.
It turned out that I was pinching the digitizer flex cable and causing it to break. I remembered from last time that i needed to cover all of the exposed copper and circuitry, but I just couldn't work out what i was doing wrong until finding this page.
Each of the digitizers appeared to work fine up until I tried mounting the screen. In the end I placed a bit of UPVC electronic tape either side of the flex cable (hoping to give it a little more strength).
When mounting the screen start with the top of the device leaving yourself a gap at the home button end. This way you can see how the flex cable is bending. I used a spudger to gently encourage the flex to bend into the cavity where the LCD cable is.
Be very careful though as one of the screens popped up slightly and i pushed it down again not realising that the flex had got between the glass and frame again. DOH....that was onto screen 4
This is a really frustrating repair, but it would definitely pay to invest in better quality screens.
Does anyone have a decent supplier in the UK?
MAny thanks