Gearing vespa t5- problem

hello friends

I've got a problem on a vespa t5 engine.
It is as follows:
third gear does not come with the rotating motor and the shaft that comes from the
cruciform is all worn out (this is the shaft:  http://www.sip-scootershop.com/EN/Products/87040000/Selector+Rod+for+Vespa+PX.aspx )

The dial is new.
Someone able to tell where the problem is?

Greetings from Portugal.