When a URL is not found in DSpace XMLUI, a very large error trace is produced in the Cocoon logs. This leads to lot of unnecessary io, disk utilization, and administrative confusion.
This appears to be happening due to the solution implemented for
DS-768. This was the old issue where Cocoon was giving a 200 error for all pages, even those that should return a 404. It was determined at the time that throwing a ResourceNotFoundException from PageNotFoundTransformer.addBody would cause Cocoon to produce a 404 HTTP response code consistently. However, this had the side effect of spamming the Cocoon log with large error traces.
See related thread on dspace-tech, which also explains some of the history: