[ODE] Mismatching results / non-deterministic behaviour

[gl]

> I've skimmed over the code quickly and there are quite a few rands in 
> there.
However, so far, the ODE seemed very deterministic to me...

IIRC the iterative solvers' stability benefits from the body processing 
order being randomised each step.  That's why you need to set the same seed 
to get the same results.  There was a define somewhere that allowed you to 
disable this, but it should work much better left alone.
--
gl