While dumping the cache during a cache stuck clean situation, the system took an assertion failure. The console output of the failing job is: http://build.wiredtiger.com:8080/job/wiredtiger-test-format-stress/65894/console.
The job is identified by Jenkins as a cache stuck clean but ending up at an assertion failure is new.
Dumping the cache does not acquire locks so maybe this is just a rare situation where that matters. The initial failure was the full cache.