only twice did my 6 sort of drop calls, once to a contact in a car on the move, which was not entirely unexpected or the fault of my phone and the other was when the auto reboot took place turning my phone off mid call...
dinolardi I put my SIM card in another phone running LineageOS → calls work perfectly. This confirms the issue is specific to GrapheneOS.
No it does not, it tells me your P6 may well be the problem. Maybe your phone hardware is failing IE the modem, dropped your phone once too often etc...