Hi,
Perform diagnostic test as per below steps and check the report generated.
SM12 -> Goto/Extra -> Diagnosis/Diagnosis in Update and
SM12 -> “test” in OK/command window then you will see extra option in menu bar Error handling -> Diagnosis Environment.
As per note mentioned by Yuksel trace the enqueue for 10 sec and with the help of the below note you might be able to understand it
125041 - Analysis of enqueue errors with enqueue logging.
Check if the parameters are set as the link for ASCS instance
Profile Parameters for the Enqueue Clients - Standalone Enqueue Server - SAP Library
Check the below sap notes and wiki
2069753 - Infinite wait in program SAPLSENA
43614 - Lock entries remain after end of session
FAQ Enqueue Server - Application Server Infrastructure - SCN Wiki
Regards,
Prithviraj.