For example if you turn on multithreading for example Mathcad will fail to converge to an answer. I don't know if this is a Mathcad bug or something in the way the problem has be cast.
If Prime gives you an answer with multicore turned off and fails when its turned on (with nothing else changed), then there sure is something wrong (either the answer you got in the first place or the failing).
If it is a bug it probably should be reported to PTC.
Agreed. I think it would help if you succeed in creating a much shorter, simpler sheet, showing the same behaviour, when you report this.
What I do not understand however is why this problem is so numerically unstable.
The secret sure lies in the underlying equations, but as they are rather complicated, nested and contain a lot of discontinuities, its sure not easy to find the sore spot.
