Exactly as it says. I've a Blu-Ray Home Cinema system and the last few times that we've watched DVDs I've noticed the dialogue is out of sync at times then reasserts itself. Very strange. Could this be the Blu-Ray player or the DVD itself? It's so annoying when you're trying to watch a film. Ps, some of these DVDs have been bought 2nd hand by my daughter. I'm not sure if that's relevant.

Could well be the TV you are using, is it a Samsung?

No. LG telly and Home Cinema.

Have a look in the audio settings of the player as there may be a lip-sync adjusting option.

A lot of modern TVs haves theme/Scene setting (usually Cinema, Music, Sports, Game, etc).

If your TV has such a thing try setting it to Game.

This should turn off most of the picture processing which in my experience is usually the culprit.