Did you back date the modification? The legal obligation is what it is. But this is going to be based on the facts and not generalities. If you have questions on the customer's legal obligation after a modification you should be talking to your legal counsel. If you agreed to extend a previous payment after the fact rather than establishing a revised future payment stream obligation, then how were they late? It is all going to come down to what the legal documents say and what you did.
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