I think this is an unfortunate byproduct of the phone not supporting SVLTE (same as all current spark capable phones). It only has one transmit path, so it cannot connect to 1x when it's connected to LTE. The Sprint network is supposed to tell the phone to disconnect from LTE and connect to 1x when a call is incoming. This is called ECSFB. But in some areas, the network doesn't yet support this feature, so you may miss calls (because as far as Sprint's voice network is concerned, the phone isn't connected). I've read that Sprint is working to get this support to the entirety of their network, but it still isn't complete. Hopefully it will only continue to improve.
Link with a better explanation: http://www.fiercewireless.com/story/...ata/2013-11-19
I haven't noticed this problem, but I'm sure it's happening to me as well. I don't live in a very updated area, as far as Sprint's network is concerned. We don't have 800MHz (because of the IBEZ), and we don't have B26 or B41 LTE yet. Just regular old LTE B25 on most towers.
Hope this helps.