Ah, that must be it then. The water was pretty much as hot as I could get it. I really didn't think about the possibility that the heat could weaken and buckle the guts... I tried straightening out the bad ones with a paperclip, and had success with 2 of them, but the other three are no bueno. It's all good though, they had already been filled 6 or 7 times, so they lived a pretty good life!

Besides, this is all pretty experimental for all of us right now, so there's bound to be some casualties!
The other 5 carts worked great! After drying them thoroughly, the smell from the previous juices were gone and they looked brand new. I filled them up (using the 'spinning' method to distribute the juice) and got 30 drops in. I'm vaping one right now, and it's rockin and rollin!
By the way, I saw this update last night and had another batch that needed cleaning, so I gave it another shot. This time, I used cold (cheap) vodka for the initial flush (twice through the syringe), then very carefully flushed twice through pretty warm water (going pretty slow). Blew them out and set them on a towel to dry overnight. This morning, 10 out of 10 looked white, clean, and fluffy inside, and no issues with buckling! I'm a happy camper now, the level of clean vs the level of effort here is pretty sweet!
THANK YOU!!!