this can be sprint network issues.
all through this thread, ive seen your behavior mentioned.
all *you* can do is reset the airvana, reboot it, restart your phone, the do a prl and profile update. this just refreshes thing and gets things on the same page.
since you never hd to do this lte/cdma switch before, it would be ok to assume you dont need to know. just watch the performance over the next few days. if it does not change, or gets worse, have a talk with sprints cs about any network issues then head over to the airvana folks and have them ping your airvana. they can see how its behaving.
also could be your ISP having some issues at the moment. lots of variables that can come into play so be patient and give things a few days to normalize.