I am pretty sure the diode in question is a schottky diode which is a major part of the switching down regulator (48v to Vcc). The diode is packaged in a TO220 through- hole package which contained "thinner than normal" leads. Package vibrates, lead fractures, circuit fails.

A rubber washer will do very little to isolate the board from vibration transfer. You still have a rigid mount to transfer shock. As was discussed, a rubber grommet may or may not help but I personally feel, it would be prefered to rigid mountings.

But there can still be motion of the entire board, so any large physical component (TO220 or leaded capacitor) may still resist movement and ultimately fatigue the leads or solder joint. Therefore, they should be mechanically secured in some way.

Yes mbwalker. Stern used (and still may do?) A similar part On their trough opto boards.
515-0174-00 (resized).jpg

Which makes you wonder why they omitted them for node boards.

That's Funny. I comment the crap out of my code so I can figure out what the hell I was trying to do only weeks earlier.