Scouring the web for a way to remedy the loose burr problem affecting late-model Zassenhaus Coffee Grinders, I found just one set of instructions. Inspired by the suggestion to add a secondary bearing, I found a scrap piece of steel 1/32" (>1mm) thick to create a new bearing.
The new bearing sits flush between the burr and the bean hopper, and accepts the burr shaft with a 5/16" center hole (actual diameter 8mm I believe). The bearing plate is 65mm long by 15mm wide, with a screw hole spacing of 50mm. It is critical to center the middle hole 25mm from each screw hole, so that the burr will be centered.
To install, first disassemble the mill. Remove the four top screws and take out the top assembly. Remove the two burr holder screws. Unscrew the handle nut and unscrew the handle. Insert the new bearing and reassemble, adding small washers as required to make the new bearing sit evenly. Photo 3 shows notches made in the plastic to recess the screw heads, making more thread length available.
In testing, the additional bearing sometimes impedes the feed rate of beans a little, but a quick shake keeps them flowing. The bearing squeaks a little, so an improved version would use a brass sleeve to hold the burr shaft.