On some Redline cars produced in 1971, when the casting was made, the metal slag did not mix together properly and had too many impurities in the mix. After the car was fastened together, and the metal cooled and hardened, it did not want to stretch. It developed stress cracks all over, some deep enough to cause significant chasms that actually caused the entire car to 'crumble' into pieces. 

Some 'Crumblers' that are still intact in the present day get restored by collectors, thus erasing their history. Few crumblers still exist, and they are tough to find for those that collect these specific examples.  Both because of the crumbling problem and the scarcity of the car in general, mint intact versions are tough to find. Despite their rarity, Crumblers are typically not worth as much as their non-crumbling counterpart.

The following cars have been noted to have issues with 'Crumbling':


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