Placing blocks really fast crashes the game and breaks the save(?)

Placing blocks really fast crashed my save. I'm not sure how fast you need to go but I triggered it with a mouse macro (not sure how fast it is).

Game crashes with arrayOutOfBoundsException -1 (can't remember details because as i was about to send the crash log, the save decided to start working)

After loading the save again after crashing, it crashed again, but then worked again after loading it for a second time.