Could you provide some additional details? Is this the Japanese DH30000 or the US DH30000U? Is the recording SD via the analog inputs or HD via the firewire input?
If you are talking about an HD DVHS (HS) recording that looked good to start with and then started to exhibit 2-4 second breakup, I'd say that's not a good sign. A new machine should not have any problems playing back its own recordings. It might be the tape, but it's unlikely. I've made hundreds of recordings with Panasonic HD1000 recorders using common TDK ST120 tapes and never see any breakups caused by the recorder.
If you've been using the machine to playback VHS tapes it's possible you have clogged the heads. Try replaying the DF300 recording a few times, and if it still breaks up try one or two short passes with a JVC DVHS cleaning tape. Don't over use the cleaning tape -- they wear down the heads. If that doesn't work take 2 aspirin and call me in the morning. :)