AccountAdd_API and UserAdd_API are executed in PBA inside a transaction. Then transaction is rolled back, but user and account are still created in POA, while in PBA no account or user is created. Why?
AddAccountMemberToPEM handler of User Created event in PBA is set to be Synchronous. Check
PBA Home > System > Settings > Events > Event Types > User Created > Event Handlers > AddAccountMemberToPEM (PBA 5.5 and later) or
Home > Configuration Director > Event Manager Settings > Event Types > User Created > Event Handlers > AddAccountMemberToPEM (PBA 5.4 and earlier):
By default this handler is not Synchronous and in that case Account will not be created in POA.
If the handler was set to Synchronous for some reason - check if it is still needed. Set the handler back to not Synchronous.