This is an edge case that may occur very rarely when a partner is trying to migrate a billing block from Customer A to Customer B. To do so, removing the billing block from Customer A is necessary so that they can configure the same account at Customer B. This can sometimes result in the following error:
"There was a problem deleting the billing block. Please refresh the page or try again."
If this occurs, follow the steps below:
a. Note down the billing block configuration and the Custom Price Book.
b. Disable the "Partner Generated Billing" option. (This will remove all PGB configurations)
c. Reconfigure the required billing block again at Customer A if necessary.