Well, I tweaked away with only the left hand catcher built and managed to get both Dillo's to fly out towards there respective portals, built the right hand catcher and now it fails completely. This is clearly a bug which I have found before but not in such a severe form, the example has been sent to Peter. It seems that when certain materials are connected to steel plate which is supported on anchors it changes the collision response of the steel plate and everything that is linked to it. In this level it effects the Dillo's bounce as it runs down the curve and has the effect of slowing it down.
I hope I can save anybody having to suffer the same frustration. You should be OK if you connect any material to the anchors before trying to get the Dillo's to their portals. Basically, build everything first then adjust it.
EDIT. I just discovered, even adjusting the length of a bar connected to an anchor changes the movement of the Dillo's. Good luck