Optimisation of helical antenna in CST

I am using CST 2015 and am trying to optimise a helical antenna but it does not like the reference WCS point it is given so it deforms the shape and moves away from the feed, because of this error it throws me back in the history list to a time before the feed was introduced and I have to create it all over again.
I have tried several locations for the WCS point such as the centre of the ground plane, the start & end of the helix but none of them seem to work.
I am presented with the error 'No point picked for WCS movement point' there is no help in CST for this error.

Thanks

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