Intermittent notifications from phone calls and Messages

Both my girlfriend and I have been having issues with receiving phone calls and text messages but not getting notifications sometimes. It's hit or miss... Sometimes my phone will ring, other times it won't. Sometimes a new message (doesn't matter if it's iMessage or SMS) will light up my screen and play a notification sound, other times it wont.

I've tried what I could find online. No the alert slider is not set to silent. No there are no focus modes on. I've ensured that "Hide Alerts" is not turned on for contacts. I even tried resetting the settings (what a headache that is). However the issue still persists.

It's very odd, there's seemingly no rhyme or reason as to when it happens. Doesn't seem to be a delay with the messages. If I send myself a message from my google voice it says I got it when I got it, and it's there when I wake up my phone. It does seem like notifications consistently make sound when the phone is unlocked and I'm using it, but that's when I need them to make sound the least...

Like I said earlier, both my girlfriend and I are having this issue, which leads me to believe it's yet another iOS bug.

Has anyone else experienced this and found a permanent solution?