After many attempts I probably found the source of problem.
I noticed that after phone reset to the factory settings everything works fine, problems appear only after restoring the settings and data from the Xperia backup (Settings > System > Xperia™ Backup & Restore). There we can backup and restore folowing elements:
- Contacts
- Conversations
- Call log
- Calendar
- Email accounts
- Wi-Fi accounts
- Device settings
- Applications
- Xperia Home layout
By recovering each of the backup elements one at a time, resetting the phone to the factory settings each time, I found that the "Email accounts" data restore results in incorrect SMS communication with the car radio.
I have 5 email accounts defined (POP3 and Microsoft Exchange) and all of them have been recovered with Xperia backup. After several tests, it turned out that it is enough to delete one of these five accounts to make SMS communication with the radio work properly. No matter which email account.
This problem is 100% reproducible, regardless of whether I manually configure an email account or restore from the backup, each time the result is a communication disruption.
My conclusion: no more than 4 email accounts can be defined in an email application.
I don't know what is the relation between the email application and SMS communication with car multimedia, but in my opinion that there is a bug either in the Sony email application or in Oreo.
