Chosen Solution
I have had screen, charging portbatery and home button replaced. Apple support have saidtbey think the phone was not original when I bought it. I did buy online. Apple support have said they think it is motherboard/ logic board problem. Theythink costswil be morethan replacing
Yes, a common cause is one or more lose solder balls that cause a break in a connection between the baseband chip and the logic board. What happens as a result is missing IMEI / Modem Firmware (Also when dialing *#06#). It will cost more than buying a second hand iPhone 6 which makes it economically viable for repair as it requires a micro-soldering technician to do the repair. I would guess at least $80-120 USD.
