Why does my Iphone screen time limit only sometimes give me the 5 minute warning?

Ever since the phone updated allowing you to manage screen time, my phone has been on and off about giving the 5 minute warning even though it's supposed to do it every time. and I know I should be able to manage my own time, but sometimes I lose track of time, but don't we all? So in that situation a 5 minute warning is nice, because then I can be more conscious of not going on it, and saving those last few minutes for something important. Cause If i'm having a conversation with someone and i Get the warning I can let them know that I have to go cause my phone is almost out of time, but with no warning, it just shuts off in the middle of my conversation and thats just not something i wanna deal with. So if anyone knows how to fix that please let me know cause it's really getting on my nerves. Either have it give the warning every time or don't give it at all, none of this sometimes I will, sometimes I won't. And does anyone else have this issue? Thanks.