Ok, for completeness, I installed v47 on March 3rd.
By checking my call history I can confirm that my carkit worked fine until end of April using v46.
One unusual thing I did today was disabling/enabling bluetooth accidentally using bluezwitch. Normally I just leave bluetooth enabled all the time.
I think, but am not 100% sure, that I rebooted the phone while I had the problem which would be like the same as re-enabling...