Very similar experience - our contract from selling the previous house was paid off about a month ago, and my wife went to pay off the Wells Fargo mortgage on this house - from a Wells Fargo account - and they wouldn't take the whole payoff at once.

I am assuming that has something to do with the insane complexity they have created with all the bizarre "financial products" in existence, that covertly encumber even simple transactions.

You never change things by fighting the existing reality.
To change something, build a new model that makes the old model obsolete.
R. Buckminster Fuller