Chosen Solution
D85 Botvac is working fine, but now has a loud knocking/clunking sound when maneuvering. It is intermittent. I service clean the brush and bearings almost every run. I have tightened up the wheel hubs, so that is not the issue. At a loss.
So the clunking turned out to be the brush motor becoming loose from the brush gearbox. I removed the gearbox from the D85 and put blue thread-locker on the motor mount screws. I also added a thin nylon washer between the main transmission gear and the gearbox. Everything is perfecto now.
