Seems mobs are forgetting they are leashed in a fence. The AI makes mob walk distant of the fence, and then return near the fence, and make it in a loop. This video explain better.

What was expected
The leashed mob walk around the fence

What occours
Mob try to go far from the fence

How to reproduce

• Leash a mob with a lead
• Click on a fence to tie it in the fence
• Note that the mob go far from the fence

(sorry my bad english)