You can enable WCF Tracing in the Core Service's config file (
web.config depending on the Core Service endpoints which are used).
These config files contain comments explaining how to enable WCF tracing and how to read the trace files.
However, the event log message clearly shows that the problem occurs in the SDL Web Batch Processor service (which processes batches which are typically created when a user performs an action on multiple items in the CME).
The batch processor service impersonates the user who created the batch. It also performs some actions using a sysadmin account which is configured in