Kryptonite lock falling apart?
Yes and no. 

Yes, that’s how they’re constructed - as two concentric pipes for strength. 

No, as in they shouldn’t come apart that easily. You may have lost a retaining screw that keeps them together. You could also just glue the two shells back together with some metal epoxy, taking care not to foul the locking mechanism. Just a little epoxy is all you need as the strength of the lock is in how the lock shackle passes through the external cylinder. You could even flex- or duct-tape them together, again the lock strength is in the shackle passing through the two shells.

If you’re under warranty, you should get it replaced though.  That’s what a warranty is for.