Obviously not in this case. I've heard other horror stories. But not with Grolsch washers and a thick strap. My straps are actually a PITA to remove so I just leave them on all the time.I have been always under the impression that Schallers are the best because of their design; even when the lock fails, it is still holds the guitar with the U shape carve.
For me, beer washers are fit and forget.Schallers are fine when fitted correctly and checked for tightness every once in a while, they are not "fit and forget". You don't drive a car without sometimes looking at the tyres to make sure they aren't flat or bald, so like anything with moving parts they should be checked.
I want to hear what your luthier finds. That is not where headstocks usually seem to break and the cracks usually follow the grain in a straight line. Did your guitar hit something on the way down that could have scratched it? If that crack was bad enough to go across the grain you would expect to see damage on both sides. Do you see any movement at the spot of the damage?I always use Schaller. Hmm its a break okay... well i'll go and fix it by a Luthier. Thanks for replies