iPhone 4 proximity sensor not working after replacing BLACK GSM
I own an iPhone repair store. I have done 100 or more iPhone 4 front glass assemblies. Those first 100 went on without a hitch. Now suddenly, in the last 3 months or so, 70% of my front assembly (screen, digi, LCD) repairs/replacements turn out great as usual, but the proximity sensor doesn't work. And I have ordered good quality glass from 2 of my suppliers.
I test all of the phones before I begin to make sure that they are working prior to my repair. Here is a scenario from today.
1. Test proximity sensor in customer's iPhone 4. Works fine.
2. Put mine in and test it. Does not work.
3. Put 3 more glass pieces on, but they do not work.
4. Put customer's broken piece back on to test (not broken in proximity area), and it works just fine.
Now, I have had this issue in the past and have examined my glass to no end. The proximity area of my aftermarket glass is just as dim as the OEM glass. And what's even stranger, is that I can put the glass that didn't work on another phone tomorrow, and there is an 80% chance that it'll work.
I have NO idea what is going on. The ONLY thing that I can think of is to get that little piece that separates the ambient light and the proximity sensor on the OEM glass and put it in there?
And is a sharpie gonna fix this issue?
I am TOTALLY lost at this point. What can I be doing wrong?
Is this a good question?