junk prefix on some VTS_01_1.VOB files

[tmoran]

Every once in a while I get a VTS_01_1.VOB that vlc won't play. "debug" verbosity says the file doesn't look like an MPEG PS file. Sure 'nuff, there's an extra 0xA0000 bytes of stuff before the pack header and system header, and the first 11 bytes in the file spell "DVDVIDEO_TS". Cutting off the junk prefix results in a working VTS_01_1.VOB file. But the guy who sends these (occasionally) bad DVDs says he's doing nothing different. What might cause this symptom - what can I tell him to change in his procedures?