Dear Lee,
Please send me the neg, marked for my attention at ILFORD Photo Mobberley: I have spoken to our technical people and they tell me it sounds like a breakdown in the cyan coupler, but we have no idea why, best guess is something to do with the processing but not in the fix.
We are also doing a test now to see if we can replicate the effect, XP1 did suffer from 'greening' caused by formaldehyde contamination post processing ( usually from foam in camera bags ) but XP2 Super is much more robust so we need to dig deeper.
we certainly have not seen this before
Regards
Simon.