I don't know if we're going around in circles or not, but here is Paypal's latest response to the issue. There is also an attachment:
Our internal team has done testing and replicated the issue. Based on the logs you have sent me, tt shows that your site is still passing the "+" sign in the address field. Please look through the attachment I have sent you the replication of the address and the error message.
Please feel free to update me again if this is fixed."
Merchant Technical Support