I could find nothing in the user manual related to what you're seeing.
Given no one else reading your thread has experienced this, I would first suspect another app doing this, like if you recently installed some Contacts app, or whatever you installed just before the day you first encountered this problem.
If it's not another app or launcher, then it's LG code or Android code. I've never seen this on any of my three different LG Android phones, nor seen this problem reported anywhere. Maybe Google the exact message?
If you think it might be another app, but don't know which one, I'd start the slow process of isolating, by uninstalling recent apps one-by-one and testing incoming calls.