Recently when I've got into my car, started and driven off, after a few seconds the audio stops and the green phone symbol lights up on the Columbus display -- when I switch to the phone page it's calling "unknown number" (but not making any ringing noises), if I terminate the call everything goes back to normal. But my phone (OnePlus3 connected via Bluetooth) doesn't show any outgoing call in the call log, it's as if the car thinks it's making a call but the phone isn't actually doing it.

 

Any ideas? Looked for any options on both car and phone that could affect this but can't find anything...

Hmmm oddly mine did this too on a few occasions but hasnt since. I was also using a oneplus phone. Oneplus 3T, it hasnt done it it a long long time and i am now using the oneplus 7pro and no issues with that so far and i have had it since launch day