This is an edge case that may occur very rarely.
Use case:
A partner is trying to migrate the billing block from Customer A to Customer B. To do so, they have to remove the billing block from Customer A so that they can configure the same account at Customer B.
Error:
"There was a problem deleting the billing block. Please refresh the page or try again."
Workaround:
a. Note down the billing block configuration and the CPB.
b. Disable the "Partner Generated Billing" option.
c. This will remove all the PGB configurations, and we need to reconfigure the required billing block again at Customer A if necessary.
d. Submit a JIRA for engineering to investigate the block deletion error.