When attempting to optimise a world created in 1.12.2 into 1.13 the readout indicates 'Failed' before optimising a single chunk. When the world is opened it generates the world as it was brand new, deleting all my builds.
When I try to open the world without optimisation the same thing occurs, I am spawned in my last position, but the world has regenerated to an 'as new' state.
When attempting to Optimise - Game output error reads:
|Error upgrading world
Complete log of both situations attached.