I have 2 Philips DVDR 3400's with the same problem. I record from DirecTV HR-22 in 480i on component video lines. My problem is the same on S-video lines.
After 5 minutes of recording the lip sync begins to slip until it is nearly 5 seconds late to picture, ( a door slams on screen and you hear it later).
Once the sound is later than that it will stutter in a way that you hear a half second sample echo for 2 seconds. "My name is John" sounds like "My, My, My, My, My, is, is, is, is, is, on. on. on. on. on. " with half the sounds omitted.
During recording the sound is effected. Stopping the record resets the sound to proper sync and the new recording is fine for 5 minutes again.
Both machines are like this now but were not like this before.
I had original (dated 2006) firmware V08.00 & V08.08. After upgrading I have V09.11, dated 2008. The upgrade has fixed the problem.
The other problem with the machines is that most commands from the remote must be repeated twice to register. The upgrade has not fixed this.
I have two other Philips DVDR's, a newer 3505 and older 615.
The newer one has much improved user interface but no component inputs. Terrestrial ATSC recordings are superb.
The 615 has a problem finishing a long recording and then writing DISC MENU. When this happens the disc is finalized as EMPTY and ruined. If a short recording is initially successful the long record is possible.