Yes, Catuva21 mentioned problems with build numbers with security patch 09.2018 and higher, logically, in this case, you need to install Morfuz on FW with a lower build number (e.g. .126, .136 etc.,), if you don't want extra problems.( The same problem was on Mate 10 Lite running Morfuz ROM). The phone issue persists on FW with Google patch 09.2018+ , so if you want to definitely solve the problem with incoming / outcoming calls, downgrade build number to .126 or .136 via Service ROM, then simply install 4.5 version , without Morfuz kernel (if you want switch processor power and change governors, you can use Kernel adiutor apk)
So there is somehting I don't understand Alf. I have flashed down to 126.96.36.199(C432). OS working. So then I have to flash Morfuz ROM 4.5. When installing a ROM, as per the instructions, one normally through TWRP
Then wipe Dalvik, cache, data, internal storage, system
And after that you flash the ROM and then do a dalvik/cache wipe and reboot.
So how does the security patch level work? Is the security patch level not tied to die System partition? When you say Service ROM, what is that exactly. I used the following ROM and installed via dload method L01-L21-(C432)-135