A small revision to the ball bearing assembly is the addition of a labyrinth hair seal and also the elimination of the copper washer. The seal results in a substantial reduction in hair maintenance.
I added a short length of ½” copper pipe to the existing flare by soldering. The outside diameter of 5/8” copper pipe is 15.88 mm which is slightly under the original Botvac
ball bearing diameter and it fits inside the original ball bearing plastic mount without touching the mount. If the 1/2" pipe it is not centered after soldering you can always sand, file, or grind it smaller so that it fits correctly. With the new seal it is more difficult for hair to reach the non rotating axle shaft and tangle around it. I will keep a weekly eye on it for a while but I am expecting a much longer maintenance time span something like once or twice a year.