Nope! I think there may be several issues related to several things going on.The only thing that actually works is fully closing out Messages when you're done with it. That's the only way I receive notifications for all of my messages. It has NOTHING to do with Android, or groups, or Bluetooth, etc. If you leave Messages open, it is showing the last message as read like you're still in the app, even though you may not actively be using it. This is a huge issue that Apple needs to get figured out ASAP. I've been looking at other phone options, but I don't want to switch, if they would just pull their heads out of their collective rears and fix this. This is a huge problem for a core function of a phone. It's nearly as bad as not as receiving phone calls.
If I leave messages open, or if I completely exit it, I will NOT get a lock screen notification (but only from certain senders) as long as bluetooth is on. On the other hand, I do get them from certain other senders. Once I turn bluetooth off, I get the lock screen notifications 100% of the time from ANY sender.
For me, it has nothing at all to do with whether or not messages is still open.