A number of years ago, some friends had a Winnie class A and began getting foul smelling water from their shower head. Long story short, it turned out to be a leak between the Motoraid and the fresh water that was being heated. We disconnected the hoses from the Motoraid, and blocked them off and the problem went away. They lost the Motoraid heating, but didn't have automotive antifreeze in their fresh water system.
Don't know if this kind of problem could have any relation to yours, but I do know I don't like Motoraids.