The ofonod-cpu-guzzling-problem is wellknown and monitored. Hopefully a fix for that behaviour will be adressed for the next update(s).
As workaround you can restart the service:
devel-su systemctl restart ofono
Works for me every time it occurs.
In my case it will be triggered once a cold-boot/restart session.
WLAN<->Mobile Data/Bluetooth-Connection/Disconnection seem to trigger that.