Mmmmm, let me see... I once worked as a rep selling/servicing/installing automotive machinery, like re borers, crankshaft grinder and surface grinders etc. We were selling newly imported AZ(Alvise Zanrosso) machines.

This one particular VB150 boring machine had one boring bar that would shudder when boring, and as a result screw up the bore so much that you had to bore it to the next size up. Well after an inordinate amount of time trying to adjust it, and having given every one in the shop a go, I completely lost it after trying again, and threw it across the workshop floor. It skid out the door onto the side walk.

The shop went quiet, and every one was waiting for my boss to fire me. Luckily my boss was Italian, and completely understood my anger... He actually laughed his ass off.

So after standing around a while I went and picked it up, and fitted it to the machine again. Lo and behold, it didn't shudder anymore, with no extra adjustment. To this day it still works like a charm. Now explain that to me...

EDIT: TYhis is the particular machine I'm talking about, VB150