Why does my samsung galaxy A5 sometimes receive text messages late?

[Shaggy15]

Lately my Samsung Galaxy A5 receives texts messages late every now and then. I'll be texting someone and then all of a sudden I get a delayed text from them that I discover minutes later. I'll be sitting right by my phone and hear no notification and there will be no evidence of a new text on my phone. I don't notice the new text until I physically open up the conversation with that person.

Any ideas how to fix this problem?