Adobe 6.5.15 uploading an asset that already exists in the DAM
When I upload an asset (tropical.jpg) to the dam and the asset already exists in the dam and I select Keep in the UI Dialog: Duplicate Asset Detected the following trace is recorded in the error.log.
The image in Dam stays forever in status Processing...
There are two workflow status entries recorded in the Workflow Archive. One is Completed and one is Aborted.

Any suggestions what could be the cause and where should I troubleshoot?
10.07.2023 08:21:15.703 *INFO* [oak-repository-executor-1] com.adobe.granite.repository Service [8728, [org.apache.jackrabbit.oak.api.jmx.SessionMBean]] ServiceEvent REGISTERED
10.07.2023 08:21:20.127 *INFO* [[0:0:0:0:0:0:0:1] [1688970080054] POST /content/dam/templates/test2.createasset.html HTTP/1.1] com.day.cq.dam.core.impl.servlet.CreateAssetServlet Marked asset /content/dam/templates/test2/tropical.jpg as duplicate.
10.07.2023 08:21:20.141 *INFO* [Apache Sling Resource Resolver Finalizer Thread] com.adobe.granite.repository Service [8728, [org.apache.jackrabbit.oak.api.jmx.SessionMBean]] ServiceEvent UNREGISTERING
10.07.2023 08:21:20.141 *INFO* [JobHandler: /var/workflow/instances/server0/2023-07-10/update_asset_22:/content/dam/templates/test2/tropical.jpg/jcr:content/renditions/original] com.day.cq.dam.core.process.GateKeeperProcess execute: terminated workflow for duplicate asset - /content/dam/templates/test2/tropical.jpg
10.07.2023 08:21:20.143 *ERROR* [JobHandler: /var/workflow/instances/server0/2023-07-10/update_asset_22:/content/dam/templates/test2/tropical.jpg/jcr:content/renditions/original] com.adobe.granite.workflow.core.job.JobHandler Error executing workflow step
java.lang.NullPointerException: null
at com.adobe.granite.workflow.core.job.JobHandler.process(JobHandler.java:404) [com.adobe.granite.workflow.core:2.0.240.CQ660-B0017]
at org.apache.sling.event.impl.jobs.JobConsumerManager$JobConsumerWrapper.process(JobConsumerManager.java:502) [org.apache.sling.event:4.2.24]
at org.apache.sling.event.impl.jobs.queues.JobQueueImpl.startJob(JobQueueImpl.java:351) [org.apache.sling.event:4.2.24]
at org.apache.sling.event.impl.jobs.queues.JobQueueImpl.access$100(JobQueueImpl.java:60) [org.apache.sling.event:4.2.24]
at org.apache.sling.event.impl.jobs.queues.JobQueueImpl$1.run(JobQueueImpl.java:287) [org.apache.sling.event:4.2.24]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)
10.07.2023 08:21:20.143 *ERROR* [JobHandler: /var/workflow/instances/server0/2023-07-10/update_asset_22:/content/dam/templates/test2/tropical.jpg/jcr:content/renditions/original] com.adobe.granite.workflow.core.job.JobHandler Error processing workflow job
java.lang.NullPointerException: null
at com.adobe.granite.workflow.core.jcr.WorkflowManager.setWaitingToAdvance(WorkflowManager.java:562) [com.adobe.granite.workflow.core:2.0.240.CQ660-B0017]
at com.adobe.granite.workflow.core.job.JobHandler.process(JobHandler.java:432) [com.adobe.granite.workflow.core:2.0.240.CQ660-B0017]
at org.apache.sling.event.impl.jobs.JobConsumerManager$JobConsumerWrapper.process(JobConsumerManager.java:502) [org.apache.sling.event:4.2.24]
at org.apache.sling.event.impl.jobs.queues.JobQueueImpl.startJob(JobQueueImpl.java:351) [org.apache.sling.event:4.2.24]
at org.apache.sling.event.impl.jobs.queues.JobQueueImpl.access$100(JobQueueImpl.java:60) [org.apache.sling.event:4.2.24]
at org.apache.sling.event.impl.jobs.queues.JobQueueImpl$1.run(JobQueueImpl.java:287) [org.apache.sling.event:4.2.24]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)
10.07.2023 08:21:20.143 *WARN* [sling-threadpool-6ad428b2-c1a0-4e82-8239-926766440932-(apache-sling-job-thread-pool)-23-Granite Workflow Queue(com/adobe/granite/workflow/job/var/workflow/models/zkb/dam/update_asset)] org.apache.sling.event.impl.jobs.queues.JobQueueImpl.Granite Workflow Queue Failed job Sling Job [topic=com/adobe/granite/workflow/job/var/workflow/models/zkb/dam/update_asset, id=2023/7/10/8/21/db5240f2-48b6-4c2a-b92c-6627c69a3d10_32, properties=slingevent:application=db5240f2-48b6-4c2a-b92c-6627c69a3d10,jcr:created=java.util.GregorianCalendar(Mon Jul 10 08:21:20 CEST 2023),slingevent:created=java.util.GregorianCalendar(Mon Jul 10 08:21:20 CEST 2023),event.job.queuename=Granite Workflow Queue,event.job.queued.time=java.util.GregorianCalendar(Mon Jul 10 08:21:20 CEST 2023),jcr:createdBy=sling-