Physics (Joint) different in build to in editor

I've build a physics experiment that creates different wave forms using pendulums of different lengths and simple harmonic motion...

It all works fine within the editor however when I export there is one pendulum that swings far more than the rest and i've no idea why...

The only difference between the pendulums is the length of the "string" they are attached to...

Anyone have any suggestions?

I've uploaded a preview of it here