This will sound weird but you can try this temporarily as I've heard it help others:
Go to your Google Now Voice settings (Google App > Three Lines > Settings > Voice) and turn off the Bluetooth headset setting.
Also, try going into Settings > Apps > Android Auto > Permissions and make sure that Android Auto has permissions to read SMS. However, Facebook would be unaffected by this.
Go to your Google Now Voice settings (Google App > Three Lines > Settings > Voice) and turn off the Bluetooth headset setting.
Also, try going into Settings > Apps > Android Auto > Permissions and make sure that Android Auto has permissions to read SMS. However, Facebook would be unaffected by this.