Ringa,
That's interesting, the cable tie is effectively fixing the rectifier slightly more rigidly to the chassis, rather than allowing the bobbins to absorb all the vibrations (I guess?).
Atalante also said he has removed the bobbins all together (simply fixing it in the original position without bobbins I presume?) and experienced no issues.
Combined with your original post, I'm starting to think you're right: the reason for rectifier failures is more linked to stress fatigue on the wires than failure of the actual part.
Maybe the bobbins aren't needed? Or would that invalidate the warranty?
I do like your cable tie solution though!
