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Do you notice any thing tht you do every time that cause the crash?
Usually when we crash it is because there are too many entities, but it also happens without a valid reason, for example while playing in vanilla (little lag, few entities, good connection).
And i will (googling) your proplem when i have a free time try to google it to
You're too kind... I feel guilty if i let you do it.
i still (googling)
but i think if you do /lagg unloadchunks , it will unload unused chunks in the worlds you have so it will no spawn mobs in the unused chunks but don't worry every chunk at least you put a block in it will not unloaded
THANKS 
ok but tell me if any thing happened
that solution come on my mind when i read the thread again and see that you have 10 worlds and you say maybe because entities spawns so i tell to unload chunks
