This is what I've seen - I ripped and encoded an album with Lame VBR nogap, and uploaded it - no gaps. Then I added VBR headers to these same files (using Mark Lords mp3tool, IIRC) and uploaded into a different playlist. The new playlist had gaps - very tiny ones, as I mentioned before, almost like a click.

I tried this. I took the utterly splendid As Heard On Radio Soulwax Part 2, which is a continuous mix, ripped it, and encoded all the tracks using a single lame --nogap command. I uploaded it and it played completely gapless. So far so good.

Then I added a Xing VBR header to each track with Vbrfix v5.2.10. I uploaded them again, and found there were tiny glitches between each track.

After several hours' fiddling with the player code, I checked the files in a text editor. Vbrfix had removed the final frame of many of the files: the gaps weren't at the beginnings of tracks but at the ends.

Mark Lord's mp3tool doesn't randomly drop frames on the floor, but will only repair an existing VBR tag, not create one.

This left me with hacking Lame not to automatically disable VBR headers in --nogap mode (line 667 of lame-3.92/frontend/main.c). But its VBR headers are invalid and they need fixing with mp3tool. With that all done, I did get gapless VBR playback with proper headers on the current player build.

Peter