Every time when I try to complete a Mob Hunt Quest it not give me the reward after I kill 5 Pigs for an example.
If I kill the sixth pig the reward bottom can be pushed. Same with auto claim you got the item one Kill later. The same is with Sheep's I tested it. For me it looks like the final Kill updates the Quest and complete it but without give me the reward.

Using:

Minecraft 1.7.10 Forge 1614
BetterQuesting-1.0.92
StandardExpansion-1.0.68
Questbook 1.1.0
RFExpansion-1.0.7
Theme 1.0.0

Found the cause of this. Turns out it happens with meeting tasks too. I'll be pushing an update to fix this pretty soon.

EDIT: Fix posted. Closing issue