I just purchased the Note 4 one week ago and am having text notification sound issues. While texting with a contact, if they reply and I still have the convo window open, the phone doesn't chime or vibrate. I keep missing replies because the phone doesn't notify me of msgs. I was having the same issue for the last few months on my S3, but figured it was just because the phone was old and not working properly. My Note 4 is brand new, so I'm guessing this is an OS problem. Nonetheless, I'd really like a fix as its incredibly annoying to repeatedly miss texts. I'm using the stock messages app, not very messages+.