Classification for the orders is currently blocked

What causes this issue?

You are attempting to create or change an order and classify it at the
same time. The order is assigned to class <ZH>SAP_KKR_CLASS</> (class
type 013).
However, the entire class is currently locked.

System Response

You cannot create or change the order while the transaction that caused
the lock is still running.

How to fix this error?

Wait until the transaction is finished. Transactions that lock the
class for extended periods of time should not be run during normal
online operation.
You can find out who is locking the class with transaction SM12:
Search for locks for table KSSKX. In the subsequent list, search for
lock argument <ZH>013SAP_KKR_CLASS</>.

Error message extract from SAP system. Copyright SAP SE.