Howdy Aussie TandeMates!
Lots of ifs, ands or buts . . .
Our suggestion: Ride the tandem! If things work fine, leave it alone. Componentry/frame are all important; however, enjoying what you've got is doubly important! You apparently got a great deal on a very much upgraded used C'dale. There just are not too many sub-30 lbs C'dale's around!
Our policy has been: buy the best you can afford, then go ride. If something does not work properly or eventually wears out, then it is time to replace whatever it is.
Enjoy . . .
Pedal on TWOgether!
Rudy & Kay/Zona tandem/USA