At a former employer, a fresh CADdie designed a brake housing with a bolt circle too close to the outside diameter for a socket to fit over the bolts. Oops.

He'd apparently turned off some constraint check without noticing, and, never having worked in manufacturing, didn't think twice of it.

The workshop foreman had to have sockets machined down in order to install the brake packs effectively.

That designer didn't dare venture into the assembly hall for years!