Took me a while to find it but I had a problem in this world where whenever I'd go past a certain point, the tps would freeze. Eventually I removed Alex's Mobs to see if that would change anything and I was able to run the game just fine past that certain point.
latest.log
In the logs it seems like whenever I would load a Pupfish chunk it would cause the game to start saving and pausing itself.

[Server thread/INFO] [com.github.alexthe666.alexsmobs.AlexsMobs/]: Found Pupfish chunk at 1295 ~ -1632 after 44 tries
[Server thread/INFO] [net.minecraft.client.server.IntegratedServer/]: Saving and pausing game...