Why won't my LG stylo 4 let me type in my password?

[Android Central Question]

Recently, the lock system on my lg stylo 4 stopped working, so whenever i type in my password, the screen goes black for a couple of seconds, then back on to try again. It does this every time when I type it in. However, I did have my fingerprint set up, so I have been unlocking it with that, making sure not to restart my phone because after restarting, my phone allows password only. I woke up this morning to find my phone had done just that and now i cant get in. I use my fingerprint, and then it takes me to type in password for "added security". (when this first occurred, my friend tried looking for the lock settings and as soon as he clicked on it/typed in password, it blacked out on him too)

 

[B. Diddy]

Welcome to Android Central! Are you able to boot into Safe Mode? https://support.t-mobile.com/docs/DOC-37693

Also, if you have an SD card inserted, try removing it, since a corrupt card can cause all sorts of odd issues.