Im one of the newer iphone users who is still having issues with this (connects for 1-2 seconds, then disconects - sometimes (mostly)) - to me its to do with the cable chip (its not debris in the phone 12 as just had mine serviced /cleaned out by an apple repair shop), as the genuine ones which come with the phone (standard lightening at the phone end), are usb-C, where as the MG4 uses USB-A, hence you have to use a non-genuine (or older apple) cable with a USB A end - I've no proof on this yet, but have just bought a short non-genuine cable as shown above (awaiting delivery though). It always charges when connected to the car (so is to do with the data / handshaking / checking etc. - and no it doesn't work using the MG4 USB-C port / genuine cable , but does charge the phone)