I decided to create a separate post for the problem of not having enough time to unlock the screen. I don't know if this might be a cause, but after reading a post on the LG forum, something hit me! I also did a quick Google search and the sensor being on has been seen on other phones, including iPhones... so it's not just Android.
In any case, here's a cut and paste of the LG thread. I found it an interesting read.
If you think about it, if the proximity sensor is on during the time you're trying to unlock the phone, and you trigger it, perhaps the screen will turn off just like when you're on a call. If that happens, then the time you have to unlock could be cut short. Possible? I don't know.
In any case, for those who are having short unlock times, it might be a good idea to check your phone to see if the proximity sensor is on. Like the LG post says, you'll need to look at it with a camera, or another phone (in camera app) due to it being infrared.
Just so you know, I've checked my phone (running Kitkat) and the sensor is "not" on during screen off time. Nor does it ever turn on at anytime during the unlocking process. I use fingerprint to unlock, and I haven't tested any other unlock mode.
EDIT... I just tested with "Smart Stay" enabled. The sensor is "not" on during screen off or any time during unlocking.
In any case, here's a cut and paste of the LG thread. I found it an interesting read.
LG g4 proximity sensor always on when screen is turned off.
If the screen is on, but before unlock, proximity sensor is on as well. It will turn off only after unlock the screen to home screen.
Will it cause battery drain and infrared light burned out/dead after being *"ON" all the time?
It is infrared, so you can only tell if you use another camera or phone look at it.
If you think about it, if the proximity sensor is on during the time you're trying to unlock the phone, and you trigger it, perhaps the screen will turn off just like when you're on a call. If that happens, then the time you have to unlock could be cut short. Possible? I don't know.
In any case, for those who are having short unlock times, it might be a good idea to check your phone to see if the proximity sensor is on. Like the LG post says, you'll need to look at it with a camera, or another phone (in camera app) due to it being infrared.
Just so you know, I've checked my phone (running Kitkat) and the sensor is "not" on during screen off time. Nor does it ever turn on at anytime during the unlocking process. I use fingerprint to unlock, and I haven't tested any other unlock mode.
EDIT... I just tested with "Smart Stay" enabled. The sensor is "not" on during screen off or any time during unlocking.