When approaching a fox I noticed it wasn't dashing away, so I kept getting closer. I noticed that it was in the same block as a bamboo tree. I broke the tree above the fox, but it stayed. As soon as I broke the bamboo in his block, he ran away (as expected).

Steps to Reproduce

1. Create a 3x3x2 of bamboo
2. Place a fox down (with spawn egg) on the ground in the middle of the bamboo
3. Put self into Survival

(N.B. Steps aren't the exact situation, but exact situation isn't know. Either way, the fox is stuck in the bamboo)