Flushing with a flush tip [from CW] thru the annode rod or drain openning and a new rod [if needed] is an annual maintenance event for me. Sometimes the rod is fine but some black, nasty looking stuff has accummulated right next to the threaded end. This black stuff may or may not contribute to the smell but I feel better with it gone.
2003 Alpine 40' MDTS
New Braunfels, Texas