I treated the solid as beam elements and when I try to determine the joints using (selecting the 'All' tic box and then calculate) , there should be a joint at one end of the shaft, but it doesn't acknowledge it as a joint although it does on the other end.
So essentially there is a missing joint.
As seen here, look to the right hand side.
**Edit - SOLUTION:**
By disabling merge results on the last extrusion of the shaft profile on that side.
Or, use weldments (structural members instead of extrusions!