I have a similar problem to one commented by @Linda A. Wingfield. When I open the world from 18w16a in 18w19b the world regenerates. Player inventory is fine, but every progress is gone. The world is as it looked when created.
Using the workaround, world opens fine in 18w15a, but when opened in 18w19b, some chunks are converted fine, and others are regenerated.
Tried several times with the same result. By placing a block in 18w15a, ensures that the chunk got converted fine to 18w19b.
Grigory Evropeytsev
I have a similar problem to one commented by @Linda A. Wingfield. When I open the world from 18w16a in 18w19b the world regenerates. Player inventory is fine, but every progress is gone. The world is as it looked when created.
Using the workaround, world opens fine in 18w15a, but when opened in 18w19b, some chunks are converted fine, and others are regenerated.
Tried several times with the same result. By placing a block in 18w15a, ensures that the chunk got converted fine to 18w19b.
The world is a default world created in 18w11a.