Is it possible to connect / join curves to an S-shape?

Hi,

We use CorelDraw to create vector files for an industrial robot and need it to follow a certian path.

We want it connected like the blue vector, but when we apply join curves in CorelDraw, we get what seems to be random results.

Somtimes we get the wanted S-shape, sometimes boxes like in the picture and sometimes a mix of both. 

Is there anyway to control this?

We often work with large files, and connecting each of them manually is a lot of work.

Is there any other tools, apart from join curves that could help with this?