Librarian sells 4 Glass Blocks for 64 Emeralds

Hey guys,

I'm fairly new to this forum but I wanted to address a bug that's really been annoying me and I haven't been able to find a solution as of now.

I have a few villagers in my base as a sort of trading hall. Everything seems fine with them except for one librarian who upped his price for 4 Glass blocks from 1 Emerald to a whole stack of Emeralds. 

I was hoping you could either tell me how I can resolve this issue or try to fix it in the next few pre-releases.

Thanks for your time,

Philip