Torpedo gyroscope icing and the limits of paper design

Why was the torpedo gyroscope mentioned in the question vulnerable to atmospheric icing?

The precise cause is not explained. The reply treats it as a design that looked satisfactory on paper but failed in practice and needed correction.

A torpedo design can work on paper and still fail under practical conditions. Testing exposes that discrepancy and creates a problem that has to be corrected. No detailed mechanism for the gyroscope's icing is supplied in this brief reply.