Mobs are lagging in a single player world, how can I fix this?

Mobs dont move properly, rather stuttering along very slowly. The rest of the game seems to run fine, and the mobs preform their animations as intended but they move at a snails pace with jittery movements as if they constantly start and stop. I've tried with 6, 8, and 10 ram and no changes.

https://spark.lucko.me/wHFltLtRhm

Here is a spark report from my game.

Thank you