John R. Carroll wrote:

(...)

Those are stress cracks that result from the molding process, plasticizer
migration and shrinkage over time.

Thanks! This plastic stuff is complicated.
Clearly I will have to turn that design task
over to a specialist.

Apparently not too much time is required
for the cracks to develop.

I shot the photo about 10 minutes after taking the grinder
out of the box for the first time. I never even turned it on.

--Winston