Game crashing when attempting to optimize world

When I attempt to optimize my world, it gets to 82% or 83%, freezes for about 20 seconds and then crashes.  I have tried this 5 times now.  I have not attempted to open up the world post-crash, I just deleted it and loaded a backup to try again.

 

My reason for attempting to optimize is that I can fix my maps in-game which has stone-like lines going through it and I saw it could be fixed by optimizing.