An update to the mcsMQTT internal broker is available at http://mcsSprinklers.com/InternalBroker.zip. The release notes to the library that is being used state "The community has fixed numerous crashes and racing hazards.". This was a problem being experienced when high CPU usage with the internal broker was identified.

I had just submitted mcsMQTT to the updater last week so missed this update cycle, but manual install will work just as well.