yes it sometimes is to do with an entity.
There are different reasons each time.
Often I will go out at night and hunt monsters (for XP, ender pearls, ect)
But often it will crash mid-fight. Which is unusual. I am only ever 4 or 5 chunks from my house where these items are stored, so that's why I thought it was to do with the amount of items.
So it's like it spawns a monster that, in turn, corrupts the game?! As I could understand data corrupting if, while saving or backing my world up to a USB (I do that incase something goes wrong such as I die with all my level-30-enchanted tools, or something like that) that any of my hardware experiences a fault. But I don't see why that would occur since I have encountered no faults with any other operation of my computer.