Here are my screenshots:

http://prnt.sc/dz3otk
http://prnt.sc/dz3oxq

As you can see, I'm somehow able to redeem for the summon scroll, and not the cave keys.
I'd assume that this means that there is a total or daily limit on how many times we can exchange for the exchange gifts, if it isn't a bug. It'd be great if you could enlighten us to what these limits might be if possible, for each 'exchange gift'.