Yes, this is a nice feature on the Fulvia which alters brake balance front-to-rear depending on how much weight is over the rear axle.
Quite some year's back I had a similar issue and since I was overhauling the entire brake system anyway I'm sure I obtained a new one from Omicron (
http://www.omicron.uk.com) rather than trying to service the existing one.
The part number should be 4178751 I think and should be relatively inexpensive (e.g.
http://lancia-parts.com/article/Fulvia/Fulvia+Coupe+S2/Brakes/4178751.html)
Regards,
Scott.