Oneplus One only working in 2G, loses carrier with 3G/4G Unless I select 2G as the "preferred network type", my oneplus one disconnects from the carrier. Not just the data connection, even the phone one.

My operator is I WIND.

It's not a SIM problem, since that same SIM works fine on my old phone, and it's not a "it's not inserted well" problem, since if I select 2G it works.

What can I do to investigate the problem? Is this operator not supported or is the phone defective, or maybe some strange misconfiguration? On the official site they claim it is supported "with limited LTE", but it doesn't work with 3G either, while I obviously assumed it did.
Updating to 4.4.4 solved the problem (it came with 4.4.2 installed).