I haven't used RWGPS too much for elevation, but every once in a while, I've found Google Maps to have an interesting discontinuity.
For example, can't reproduce it when I try now, but last summer I plotted a route on the Great Plains between Lubbock and Amarillo. The initial routes has two discontinuities where the road appeared to go from ~3700ft elevation to sea level and then back to ~3700ft in a very short distance. Clearly there isn't such a deep chasm in that area. That by itself was ~7500ft of climb that added considerably to the total for a mostly flat route.