[ONE General] vantt1:
Note: the fix depicted below is only a plausible fix and it assumes the screen/digitizer itself is not faulty. If you intend to follow it, be aware that a faulty screen can be a possibility, so RMA if you can. Unlike the other software fixes out there, tampering with the hardware is a one-way trip and will void your warranty.

Ever since I got the OnePlus One, I've been having issues with the touchscreen. Some touches weren't being registered, and sometimes when I'm scrolling, something along the way would be touched instead. Double taps turned into single taps, the camera shutter button was hard to touch, and typing was unpredictable. The list goes on.

OnePlus has addressed this issue as a "software bug" (just like the yellow tint), and promised to fix it in future updates. It worked for some, and I did notice some improvement, but it just wasn't good enough for me. I thought all the software did was merely filter or mask the effects of the grounding issue, and anticipated or extrapolated touches made by the user.

No matter which ROM or which version of CM11S I used, the touchscreen was never quite perfect. At some point, I knew for sure it wasn't simply a "software bug", because I've tried numerous kernels and ROMs, to no avail.

So, I went on a little investigation, because I'm actually quite familiar with problems like this. The iPad Mini suffers from a very similar grounding issue when the digitzer gets replaced. The original digitizers are all insulated properly from the factory, but when it breaks and needs to be replaced, the replacement screens don't come with the insulating tape pre-installed. If not insulated, the digitizer makes contact with the inside of the aluminum unibody, and thus creates the grounding issue.

The tape insulating the touchscreen circuits has to be moved over from the original, broken screen to the new screen in order to prevent the issue. See the original, broken iPad Mini digitizer (left, bottom) compared to a new, replacement digitizer (left, top):

Note how there are areas of the iPad's chassis that can make contact with the digitizer if not isolated.

I was 90% sure that something similar was going on with the OnePlus One. And I was right.

I fully disassembled my OnePlus One (for the second time), but this time around, I removed the screen as well. I didn't do it the first time because it's a risky operation; I might damage the only screen I had during the process, and it won't be as secure of a bond as before. But YOLO, right?

Here are the instructions on how to do it yourself!

As suspected, the digitizer flex makes direct contact to the metallic chassis before being connected to the logic board, just like the iPad Mini does with a replacement screen.

And sure enough, when the flex is isolated from the chassis, the problem disappeared. The phone had no problem registering all 10 touches, and every touch was more responsive than ever.

Debug mode, hardware edition!

So the fix was quite obvious; insulate that digitizer flex! I cut some of the insulating tape from the iPad Mini's digitizer and stuck it on the chassis where it was touching the flex. Any thin tape will do though.

I then reassembled the One, and as expected, the touchscreen now works perfectly. No more ghost touches, and no more grounding issue. I'm as happy as Larry :D

Why, then, did some units suffer more than others, and some received perfectly fine units? Well, here's my hypothesis. Unlike mainstream smartphone manufacturers, who either use properly isolated digitizers and/or double-sided 3M tape, OnePlus neglected the former and used glue instead.

Look closely in the image below - you can clearly see that it isn't tape that's holding the screen in place. That pattern is characteristic of unset glue that's been compressed.

It loses form and stickiness when removed. Double-sided tape retains its shape and doesn't lose stickiness.

Because glue was used, every individual phone most likely had a different clearance between the chassis and the digitizer flex.

From what I heard, the newer units have fixed this problem, but I can't confirm for myself exactly how they fixed it.

So there you have it! As it turns out, it really was a hardware problem (judging from my investigation). It would be great if other forum members can confirm my theory if they have the chance. If you:

Have a One that suffered from this issue

Have a broken screen

Want to try your hand at replacing the screen yourself

Now's a great opportunity!