Minecraft crashes while loading a local world with experimental gameplay enabled after updating to Windows 10 Skip Ahead build 18860. The world worked as intended before the update (from Build 18855.)

Loading new experimental worlds (from new worlds, or enabling experimental gameplay in existing ones) does not result in a crash

Re-enabling experimental gameplay on the original for the world that will not load and loading it does not result in a crash. 

Replicating changes made in the world that crashes on the new experimental world and loading it does not result in a crash.

Exporting and reimporting the world that crashes still results in a crash when loading. 

Attached screen capture is from the moment before Minecraft crashes while loading the experimental world.