Error: "-1.#.ND" ? What?

[Daemian]

Hello ppl,
I'm getting a strange bug when i walk the player over rocks.

Suddenly the screen goes black, the darkness tip appears "don't stay on darkness" and then you die.
After you respawn, the screen is still black and you can't use the lantern.

Then, for some reason, if you don't quit the game fast, your cpu usage increases to 100% in about 5 seconds.

This only happens when you walk over rocks, not all the time, but it happens once in a while.

I thought i was just falling off the map, but
when this bug happens the Y speed goes to a strange value: -1.#.ND
Instead of -30 or something.

Maybe the custom entity is the problem?



Thank you.

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oh, and in-game this rocks are set to Static.
And size 5.0. So, big.