[Leica] Pinkish splodge - any ideas what it could be?

[douglas.sharp at gmx.de (Douglas Sharp)]

This slide was taken on Fuji film (ASA 200) and has a pinkish area at 
the bottom.

http://gallery.leica-users.org/v/DMS/Berlin0353scan.jpg.html

It looks as if light is getting on to the film where it shouldn't. A 
group of consecutive shots have it, others don't.

Is it lens flare? It may be imagination, but I think I see it in the 
viewfinder when a Rollei 21mm lens is attached.

But:

It doesn't extend into the perforations

The Rollei 3003 doesn't have any foam light seals that could have 
deteriorated (German precision, metal to metal, with overlapping flanges 
:-) ).

It looks to me as if it got on to the film before or after exposure - 
maybe when I loaded/unloaded it or when the lab opened the film cartridge?.

Being on the bottom, I assume it must be light coming from the top.

However, the top of the film magazine is completely covered by the top 
control-deck of the camera

This could perhaps mean it's coming from the waist level finder, but 
during shooting I've always got my eye almost completely shading it from 
light while looking through the magnifying lens (shown on the 2000F at 
the left on Stephen Gandy's pages)

For those who don't know the Rollei 3003, it's shown pretty much in 
detail on Stephen Gandy's site.
http://www.cameraquest.com/rol3003.htm

I would welcome any ideas about what it could be, I hope it's not the 
camera.

TIA
Douglas