It's a "perfect storm" situation.
a) In the tolex case, the neck rests on the raised ridge, right near where the stock meets the neck. It acts as a fulcrum.
b) It's cold weather season still. Things tend to act more rigidly, less flexible when they're cold.
c) Strings tuned to pitch put a huge tension load on the neck, especially at the nut area. There is no trussrod to help the headstock counteract the string tension.
All it takes is to drop the box on its flat side just right, the sheer mass of the unsupported headstock (including tuners) is enough to snap it like a twig against the fulcrum that only supports the rest of the neck.
People always ask why big name builders always ship basses tuned to pitch, if it increases the chance for neck damage? I have no idea why they do that. Maybe they have a better way to support their headstocks. Looks like G&L just ate two in a row....with the same customer!