I have a minecraft survival world that was started on 18w22c. I died with no bed set and it therefore attempted to respawn me in the spawn chunks. Game immediately crashed. Wouldn't let me open the world at all. Downgrading to 18w22c fixed the problem and the world loaded properly in the prerelease after the chunks had been reloaded in 18w22c. However, upon attempting to reload additional chunks in the 1.13 pre1 version after fixing the initial crash, the game once again crashes and the same downgrading process had to take place in order to fix the problem. Essentially, EVERY chunk that was originally loaded from the 18w22c version causes the world to crash. Reloading the chunks in 18w22c and then once again loading those chunks in the prerelease fixes the problem only for those set of chunks that were reloaded in 18w22c.