My Galaxy S4 with Lollipop sometimes does not accept my unlock pincode I have a Samsung Galaxy S4 (GT-I9505) with Android Lollipop (5.0.1), and rarely, my pincode just fails to accept when I'm unlocking it. I pick up my phone after not using it for a few hours, enter the pincode exactly like I usually enter it, but it disappears and I get the error "invalid pincode". I try 5 times in a row, keep getting the error and end up getting locked out for 30 seconds. I've had  this situation twice so far.

The only way I found to fix it is by rebooting my phone, which means I lose everything that's not saved properly. Obviously this is pretty annoying. Are there apps that can hijack my unlock screen like that? If so, how do I find such apps? Or is there another reason for this?
That is a very odd situation.

I'm assuming that you're using the stock lockscreen, not a third party.


My first recommendation is to use a different lockscreen type. If you're using PIN, try a pattern. This is actually going to be the easiest solution.
Install Go Locker or other 3rd party lockscreen, run it once, then immediately uninstall it. Reboot, go into settings, set up your original lockscreen again.
I noticed you're running 5.0.1. Assuming you're all stock and unrooted, accept the OTA update to 5.1.1 and that should solve these weird issues.
If that doesn't work, you may have to stick with Go Locker.