They use some service to feed into their guide, it is possible they (the service, not D*) had some kind of hiccup, or missing data, or some kind of change.
Also, depending on the last reset of your stb, it could be just that data was not downloaded yet for those channels.
FWIW, I notice that when the guide updates on my D10s, after a reset, for example, that the guide updates do not seem to be strictly sequential, so they can update some entries 2 hours away before finishing updating ones only 30 mins away (for example).
Though this post does not rule out that it could be a H20 software issue.