Why hostile mobs start to spawn then all of a sudden they just vanish? Minecraft 1.10.2

Question

This is a very strange phenomenon hostile mobs will start spawning at night then all of a sudden vanish with out a trace within 2 days (Minecraft time). First they spawned regularly within the world I created then my game froze and crashed twice now when I go into the game no hostile mobs spawn at all and no crashing occurs.

FML Log

Modlist I am using

If this isn't the right place to have this answered then I will go to Minecraft forge to ask this.

Edit: Hmmmm...I'm going to check something out really quick and see if the problem is what I think it is.

Re-Edit: I found out the issue. It was that I had a mob spawn editor mod named NoMobsSpawnOnTrees. The spawns per tick was set to 0.0 so I set it to 20.0. So far hostile mobs do spawn at night now

Extra spawning tries per tick. This only applies to hostile mobs.

D:extraSpawningTries=20.0 <-- was set to 0.0 before

Make sure you set this in the settings if you want hostile mobs to spawn at night.

Answer 1

If it was not a mod pack, I would say that hostile mobs naturally despawn afer a period of time. If you move to far away from the mobs, they will despawn from that area and spawn in a dark areas somewhere around you. This point is made when testing mobs in a fortress and overworld. In the overworld, I have tested the theory that mobs despawn after you die. This is false. If you die near the spawn area or bed (if you have one), you will respawn and the mobs are still there. However, lets say you died in a fortress that is 2000 blocks away from where you spawned. After awhile of you not being near there, those mobs automatically despawn from that area just so they could spawn where you are. As for the never spawning at all, there are only 2 options. The first is that the light level is too high for them to spawn, and they instead gather in underground caves. The second is that, ultimately, you glitched your game This sometimes happens with save files if not properly shut down, and you may need to modify the file or just create a new world.

Answer 2

Part of the problem with answering your question is that it is unclear exactly what your question is.

"...hostile mobs will start spawning at night then all of a sudden vanish with out a trace within 2 days (Minecraft time)"

Your opening statement sounds like normal typical behavior. Hostile spawn and despawn based on ridged game rules. They only spawn further than 25 blocks away from the player, and less than 129 blocks from the player. once they are closer than 23 blocks to the player they cannot despawn. If the player moves more than 82 blocks from a hostile mob it will despawn. One of the ways to clear a small island for example, is to row away from the island then rapidly return before many hostiles can respawn. If the island is smaller than 26 blocks across nothing will be able to spawn on it while you are on it.

Answer 3

1. It is something to do with your mods, like something to disable mob spawns

2. They are out of range and are despawning, like above there could be a mod that makes the despawn range shorter