Audio out of sync problem

[Mp101]

It happen that I open a VOB file.
Avidemux creates the index of it.
Then I find the audio out of sync.

Indeed if I open the VOB with other tools ( like vlc) the audio is correct.

My need is to open a vob with avidemux, then to select one of the availablle audio tracks, and save as a new vob as mpeg ps a+v. Practically no conversion is required as both the suorce and the destination are mpeg2, only the selected audio track is saved.

With many vobs (all are dvds, where the vobs of the main film are connected together into a single vob) it works but in one case I have the audio out of sync.

But even before saving the vob, the audio is out of sync if I play with avidemux.

Thanks