Thanks for your help Dave.  I am running an analysis of a lift scenario; there is a large end termination being lifted, attached to a cable-type structure that I have idealised to a series of short cylindrical lengths, connected by revolute joints.  The cable has a bend restrictor that stops the joint rotating at a set angle.  The whole unit rotates from horizontal to vertical orientation as it is lifted, due to the mass of the cable hanging from one end.  I am running the analysis up to 10 m lift height, there seem to be a lot of itterations, possibly due to the revolute joints stops.  I will try deleting the output file midway, thanks for your advice!