Subtitle problem when muxing with half D1

[scissors]

Maybe someone can help me here.

95% of the time I can use vobsub followed by sup2sup to create a SUP file to mux with my 352x576 video.

However - and it's doing my head in - there are the odd titles (MASH/BAttlefield earth were the last 2) where the muxed subs are just garbage.

Loading the sub into varies editors shows they are garbage also.

So i think to myself, "the stream is comming off corrupted".

But if i mux it with 704/720 x576 video it is fine!!!.

I tried editting the IDX file for 50% width, but it seems to get ignored - but subs that work seem adjustable.

Any ideas?

[scissors]

when i say garbage they look like pixellated blobs - however you can occasionally make out what might have been text