Insofar as deposits are agreed said deposits shall be made, at BMW's option, in return for a bank guarantee by a major German bank or by a group guarantee. The guarantee must apply for any and all claims arising out of any failure to execute the order in accordance with the contract, statements of account or warranty with a waiver of the defences of voidability, set-off and benefit of discussion as well as with any possibility of deposit excluded; however, it shall not exclude any further-reaching claims. The defence of set-off does not have to be waived to the extent that the Contractor's claim is not disputed by BMW, has become ripe for judgment or has been decided and become final and unappealable