Some 3 or 4 years ago I had this fault on a Triton T80i, also fitted with Stabiliser Valve assembly 82600250. Disassembly, noting relative positions of components, revealed that a small plunger pin (about 2 cm long and 5mm diameter with a flange at one end) made of nylon or similar had snapped into three pieces. I repaired it with Araldite.
No problems until yesterday when the fault reappeared. I shall strip it again and if the same thing has happened use the Araldite or perhaps buy or make a replacement pin.
John Hodges
May 2009