I have a number of series recordings setup. They work fine for a random amount of time, couple days, week or a month then they stop working and I have to delete them all and re-add them. I usually don't notice until I have missed a few recordings of scheduled shows. The guide seems fine, it is up to date but the series show no future dates for recordings when there are a number within the next 14 days. In most cases all of the series stop recording but a few times a couple are still working and the rest are not.
Very buggy box this DCX3510-M. Due for a major firmware update I would say.