Hope it’s OK to resurrect such an old topic 
.
I’ve been having the artifact issue since I had the phone and it hasn’t been too much of an issue. But over the last couple of months I’ve been experiencing the FP2 incoming call screen freeze issue, but it is also happening with other apps.
The screen won’t respond and sometimes the image on the screen splits down the middle and one side lags a fraction of a second behind the other. Then it usually doesn’t respond for about 30-60 seconds and then it’ll show an ‘App isn’t responding’ message and I can close the app and the phone is back to normal. After that I sometimes get strange looking icons as I posted in the first screenshot here.
I’m using LineageOS 17.1.
I know your post is from nearly 2 years ago, but did you manage to fix this issue? Did the new screen help in the end? I’ve cleaned the contacts of my current screen and it doesn’t look damaged.
All the best 
.