Unlocked phone saying network locked

[bloomen]

My unlocked LG G4 from new has taken to telling me it's network locked in the last couple of days. It's sim card agnostic, doesn't matter which, a factory reset did nothing to cure it.

Nothing physical has been done to it. Nothing software wise has changed. It's just started doing it after short periods of time. Sometimes restarting clears it but then it starts again.

Can anyone think of an obvious reason?

[hutchst]

Firmware? Can you re-flash it?

[bloomen]

hutchst said:

Firmware? Can you re-flash it?

A fine idea. I did it and upgraded it to 7.0 as well.

It was fine for a few hours then the exact same message popped up. I'm dead stumped.

[LordGrover]

Have you tried another SIM card?

[bloomen]

LordGrover said:

Have you tried another SIM card?

Yup. 3, EE and Virgin. It happens on all of them and they're all sims I've had for ages without any trouble.

It's been unlocked from new. Never done this before.