Cannot receive text messages via Bluetooth in both of my cars audio systems from only one person

[ntotrr]

This is baffling me and I can't seem to resolve this. I cannot receive text messages in both of my cars audio systems via Bluetooth from just one person who happens to be my wife. I can receive text messages from anyone else properly. I do receive the messages from my wife on my phone but not the car's systems. A little background: this is not device specific. This problem existed when both my wife and I were using our LG G3 phones after they were updated to Android 6. I briefly upgraded to an LG G5 but returned the phone as it was defective and that problem still existed with that phone. I have since upgraded both my wife and myself to a BLU Pure XL that run Android 5.1. I still have the problem. After our G3s were updated to Android 6, my wife couldn't send a text message to me at all - her phone was somehow cutting off the area code even though my contact contained the area code. I deleted my contact and added a new one a few times and got that resolved to the point I get messages from her on my phone but since then, I can't get the messages on our car's audio systems. As I said, I can get messages from anyone else in the car, just not her. She receives them from me both on her phone and in the two cars. AT&T has been no help in resolving this so far. I've not even heard of a problem like this.

 

[B. Diddy]

Is she definitely sending the messages as SMS, or is it possible she's sending them as Hangouts instant messages? This would only happen if she's using Hangouts as her default SMS app. (I have no idea if a Hangouts IM might cause this problem as opposed to SMS, but just thought I'd ask.)