not sure if this helps - but i heard somewhere that if te police get a single detail wrong on an infringement notice/defect notice, it voids the whole document
cant confirm, but if they've got your rego fairly wrong you should be alright cos they could be wrong about everything else also!
try worm your way out of it and you should be sweet, but if you've gone to the effort of making at roadworthy, may as well clear it up
good luck