When Hibernate's ehcache plugin starts up, it looks for a configuration file called ehcache.xml in the class path. The main ehcache.xml configuration file is in (common/common-composite-component-data/src/java/ehcache.xml).

The Sakai help tools deploys its ehcache.xml to shared/lib (sakai-comp-shared-help-sakai_2-1-x.jar) as part of the help-component-shared deployment. The problem is that every once a while, the ehcache plugin finds the ehcache.xml in help first and loads that one instead the one in common-composite-component-data. This means that all the cache definitions are missing and every cache is configured with default values as defined in, or lacking any definition in, ehcache.xml file located in help.