Put the summary of the bug you're having here
What I expected to happen was...:
Sheep should have eaten grass. Changes grass block status to be observed and auto sheared.
What actually happened was...:
Sheep got wool back but grass stayed
Steps to Reproduce:
1. In a snowy tundra
2. Sheared sheep
3. Sheep regained wool without grass leaving
Could it either be
a) The sheep are grass through the snow?
b) Your "mobGriefing" gamerule is set to false?