[SlimRoms Q&A] onefang:
I searched, and didn't find any other posts about this, but the search engine here seemed a bit flaky.

I installed SlimKat 4.4.4.build.8.0 on my Samsung Galaxy S3, um, last year I think it was. I had previously been using SlimBean, having dumped the original Samsung ROM fairly shortly after I bought it. Since then there has been weirdness that relates to the proximity sensor.

I used E-Robot to disable the screen when anything is close to the proximity sensor. So put it face down, screen off; put it in my shirt pocket face inwards, screen off; leave it on the desk face up so I can see the screen, screen on. Naturally - hold it to your ear on a phone call, screen off, though that's a basic function of the proximity sensor, it did that anyway. On the flip side, if it was blanked and you uncover the sensor, the screen would come back on, but it would be the Lightning Launcher lock screen that I prefer. I got used to Lightning Launcher from SlimBean.

After installing SlimKat, when covering the sensor, first the volume controls show for a few seconds, THEN the screen goes off. Coming out again, the Lightning Launcher lock screen would not show. This got a bit awkward before I figured it out. I usually put my phone in my shirt pocket screen inward, so that the sensor triggers the screen disable. But now, since the volume control is showing for a few seconds first, I discovered that my chest would brush against the screen, randomly adjusting one of the volumes as it went in my pocket. Since I usually have the volume turned all the way up, the only way was down. I missed a few phone calls that way before figuring out why my phone wasn't ringing.

So I have disabled that E-Robot thing now. BTW, there's no way to turn the SlimKat screen blanker off? I would have tried that first, but could only find how to set the timeout, not how to turn it off.

More recently, though this may be a new hardware problem, but it's a big coincidence ... now the proximity sensor refuses to work at all. It always thinks it's covered. This is a really big pain, since as mentioned above, the proximity sensor is designed to disable the screen when you hold it to your ear, only now it disables it the moment the phone call starts, AND refuses to enable it after the phone call is over. The sensor still thinks it's being held to your ear, the screen stubbornly refuses to switch on, no matter what buttons I press. Only way I can get out of that state is to pull the battery. This is not good. (On the other hand, this sort of thing is why I always get phones with swappable batteries, as a very experienced computer dude, I know that sometimes you just have to kill the power.) So anyone I call gets to hear my swearing as I rip the case open and pull the battery out, before I can end the phone call. Though pulling the battery naturally ends the call. lol

About the same time I noticed the proximity sensor no longer working, I noticed the up volume button also isn't working. That could have been broken for awhile, I rarely use either volume control. Part of the reason for doing this entire proximity sensor disabling the screen thing is so I could avoid wearing out the physical buttons. The S3 is old, but I like to keep my computer hardware running for a long time.

Sooooo, proximity sensor and volume controls interact in odd ways, then both fail. That's a pretty big coincidence. Though having just written that, I have come up with a new theory. Maybe some common part of the physical circuitry for the sensor and the button was going flaky, such that the sensor triggering sent noise through the up volume control, triggering the on screen volume controls before blanking. Still, a coincidence that it only happened after installing SlimKat. Also, wouldn't this trigger both volume controls and screen disable at the same time, rather than within a few seconds? No idea how Lightning Launcher fits into this new theory.

So I'm still not sure what's causing this, or how to fix it. Other than going back to SlimBean to see if that fixes anything. It doesn't look like I can go forward, 4.4.4 looks like the last SlimRom made for the S3. At least according to OTA.

Anyone got any ideas? "Buy a new phone" isn't a good answer for me right now, can't afford it.