Some SMS Vibrate / Others Dont

[its_miller_time]

Okay team, so I am a little confused on this "bug" I've come across - or maybe it's not a bug, I don't know.

So, I noticed that for my SMS/MMS messages, some will vibrate and others wont. I have the notification settings set to vibrate but I cannot determine what makes some incomming messages vibrate and others not vibrate.

Does anyone else have this or experienced it?