I just started experiencing this same thing in the last week. Real frustrating part of it (beyond the obvious) is that there is no way to tell this is happening unless you are actively using the network at the moment the signal is lost. So if the phone is in your pocket and not being used, you'll really have no way of knowing whether you are missing important phone calls/text messages simply by looking at the display of the phone. Each time I only notice when I am trying to load a web page and it says I'm not connected to the internet (even though it shows that I have a strong LTE connection). Talked to both Google and T-Mobile about this and both basically pointed their fingers at the other. I'm pretty convinced that the problem is on Google's/LG's end though.
Getting my third RMA in the mail next week. Will likely take them up on their refund offer if this continues. Believe it or not, the intermittent loss of data isn't even the reason I set up the initial RMA (or the reason I sent back the first two RMA's I received).