2651198 - UME operation fails with "401 Unauthorized" error using Load Balancer

PI messages are failing with "401 Unauthorized" error using a load balancer and you see the following exception in the default trace:

#Error#com.sap.engine.services.security.authentication.logincontext#
com.sap.ASJ.secsrv.000198#BC-JAS-SEC#security#[...]#sap.com/com.sap.aii.adapter.soap.app#com.sap.engine.services.security.authentication.logincontext#Guest#0##[...]#[...]##0#Thread[HTTP Worker [@XXXXXXXXXXX],5,Dedicated_Application_Thread]#Plain##
com.sap.engine.services.security.exceptions.BaseLoginException: Error in some of the login modules.
[...]
Caused by: com.sap.engine.frame.core.locking.LockException: Cannot lock [I2018051301331997900000briu1971a.................<XXXXXXXXX>, $library.security.ume.core, [Name of the corresponding key]; it is in use by another owner. The lock collision occurred with user <internal>.
at com.sap.engine.core.locking.impl3.LockingManagerImpl.lockInternal(LockingManagerImpl.java:168)
at com.sap.engine.core.locking.AbstractLockingManagerImpl.lock(AbstractLockingManagerImpl.java:466)
at com.sap.engine.core.locking.ServerInternalLockingImpl.lock(ServerInternalLockingImpl.java:52)
at com.sap.security.core.server.ume.service.UMEServiceFrame.lock(UMEServiceFrame.java:171)
... 54 more

• SAP NetWeaver
• SAP Process Integration
• Load Balancer

enqueue, 401, unauthorized, PI, Locking, lock, locks, enqueue, enq, enq lock, enq locks, enqueue locks, enq server, enqueue server, SHOW_LOCKS, REMOVE_LOCK, cannot lock, ume.locking.max_wait_time, com.sap.engine.frame.core.locking.LockException, BaseLoginException, Error in some of the login modules , KBA , BC-JAS-SEC-UME , User Management Engine , BC-JAS-COR , Enterprise Runtime, Core J2EE Framework , BC-JAS-SEC , Security, User Management , Problem