You normally cannot strike anything until it is submitted to the court. Since discovery is between parties, now would not be the time. You will need to wait until they try to enter it as evidence at some point to ask for the court to strike it, and then your RCP or case law will kick in as to how and when. Some courts make you wait until the trial or a Summary Judgement attempt before attempting to challenge evidence.
If the evidence was extremely prejudicial, you could possibly file a motion to preclude, but that would not be the case for just defective affidavit or bill of sale.