Ask a Business Lawyer. Get Business Law Questions Answered ASAP.
Seller did not have the power to assign the lease. Therefore, you don't have to either. On one hand the seller could argue that the purchase price should be modified for you to pay more. I would resist this AND ANY ATTEMPT TO REPOSSESS. You agreed to a price with lease assumption in good faith assuming that the seller had the right to assign.
THE MISTAKE WAS UNILATERAL ON THE PART OF THE SELLER. That is the legal argument to use in response to any action on the part of the seller. It was his mistake. He cannot repossess or demand more money from you.
I don't feel that the notary date is the issue. Seller just didn't have the right to assign. The letter and storage idea is good. $25/day is reasonable...no WA law controls.
Include in the letter a demand for the 3 machines to be delivered in the same one week and if not.............. that you will sue for breach of contract for the value of the machines and the storage charges.