T-Mobile has started pushing out a new update to LG G3 units on its network. Arriving as software version D85130g and weighing in at 132 MB, the update brings along multiple changes, including fix for 2G/3G data roaming issues.
In addition, there's also an LG app fix as well as some stability-related improvements. The official changelog also mentions "Google monthly security patch," but it doesn't specify exactly which month.
As is usually the case with OTA roll outs, it may take time for the update notification to pop up on your device's screen.