I don't know if this is a bug or just a new feature but the limit to how much you can fill is much smaller, and you need to be very close to where you want fill for it to work. If you exceed this limit, instead of telling you your fill size is too large, it just says "Cannot place blocks outside the world."

How to reproduce:

*Fill in an area larger than 36x36 blocks using chat or command blocks

*Fill in an area from 20-30 blocks away from the player