As I mentioned, it may have some pieces of the molt it can't remove. Did the cast-off cuticle look complete, or was it "in pieces"?
Yes, crustaceans can indeed die from a "bad molt", altho I can't say whether it's similar to "shell rot" on a mantis or something different. We lost one of our mantises to shell rot, so we've seen it firsthand.
About the only thing you can do at this point is wait and see, and keep the stress down.
Are you dosing the tank with any supplements?