We are exporting them using UPS with all the correct paperwork
I'm wondering if there's not something missing here, to be honest.
What I'd do is go to a couple of clearance agents (or call them) and ask them about the procedure in this case. Something just seems wrong - you shouldn't need to complete the SAD for something like this if the export documentation was done properly. Don't take the first person's word for it - try a few until you get a clear answer.
It seems to me that you should be supplying proof of the export (via the Urzad Celny computer system, whatever it's called here) when you re-import the goods - VAT and duty was already paid at some point, so it's illogical for them to be charged twice. Do you have access to the computer systems that they use? You should certainly have access to "CELINA" - if you don't, then it makes me think that something isn't being done correctly. UPS will provide the notice that the goods have been exported, but I think you should also be declaring the export.