My Sprint 8703e also fluctuates between 1X and 1XEV at my house (mostly 1X). Where I live, I've had spotty coverage with all the carriers and, when I first got Sprint, I was worried about signal strength although the coverage map shows me square in the middle of good coverage. When I zoomed in on the coverage map by entering my house address, it showed several areas of poor coverage inside the area that was painted as good when the map was zoomed out. I live on the edge of one of the poor coverage spots.

Even in areas with good or excellent coverage outside, when I go inside some buildings it changes from 1XEV to 1X. That suggests to me it a reception issue, not software.