System error in lock management

What causes this issue?

An internal error was found in the SAP lock management system when
attempting to lock an object by calling an ENQUEUE function module.

System Response

The SAP system cannot enter the required lock correctly into the lock
table managed in the enqueue server and the ENQUEUE function module
therefore triggers an exception. If the application cannot process this
exception, the active transaction is canceled automatically.

How to fix this error?

The most frequent reason for the error message is that you can no longer
access the enqueue server. This may be caused by the enqueue server not
running.

Error message extract from SAP system. Copyright SAP SE.