[Leica] M6 scratching film

[Gareth Jolly <gareth.jolly@minters.com.au>]

I've just noticed that my M6 seems to be leaving some very fine
scratches on film.

The scratches run lengthwise across the negative.  They don't appear
on all negatives, but appear on a reasonable proportion of negatives.

They don't appear in the same place on the different negatives.

The scratches are so fine that I can't see them on a negative with a
loupe.  However, they show up on a scan when enlarged.

I'm confident its the M6 causing the scratches rather than anything else,
because negatives taken with my Nikon around the same time don't
show any scratches.

Does anyone have any experience with what might be causing this and
how it might be fixed?

Thanks in advance
Gareth Jolly