Notification bug on Steam app

[Marineer meneer]

Hi there,
So I am using the steam app for a long long time. I often get messages on my account and I will get a notification on my pc. The thing is that sometimes I will also recieve the message that someone sended me on my phone. But the phone notification seems to be random for me, because sometimes it will notify me, but sometimes it won't.
Can someone explain how this works? Or is it something in my account settings? It's very annoying, because I didn't knew someone was asking me something becase my phone app didn't nitified me, or I will get meesages on my phone AND my pc...