I'm having a similar issue with one of my Lifx lights - I have 28 downlights and I've successfully connected groups of them to several Flics via my hub. Everything worked fine on the first day, then one of the lights stopped responding via the LAN protocol. In the app it appeared in the list as an IP address rather than its name. I tried resetting the light, assigning new ip address and changing the name but no dice. I replaced the light with a spare and successfully got it working with the Flic for that room. The next day, a different light in the same group of lights dropped off the list with the same behaviour. Cloud control works fine. Control of the light works fine via the lifx app, which I assume is working via LAN as it's pretty fast.
At this stage I'm not sure if it's a Lifx issue or a Flic issue - I could replace the light again but at 100 dollary-doos that's an expensive troubleshoot. With 28 lights controlled across nine Flics and a single Hub, is it possible I'm pushing a device count limit?