B Boyes

Since being auto-updated to release 2.1.7659, the launcher has the issue where it uses 100% of the CPU. This happens whether "Keep the Launcher open while the game is running" is checked or not.

Occasionally the launcher will crash after quitting the game when the option to keep it open is checked.

Similar issue with Launcher 2.1.7659 for MacOS wherein it is stuck on the profile it was on before the latest update. If other profiles are used to launch the game it will always revert to that one specific profile on next launch.

I can confirm that generation seems to now work as expected in 19w03a. A 1.12 save opened in 19w03a, using both the "Optimise World" option and without (done on separate copies), the generation is as expected. Hopefully the OP can confirm also.

Similar to what João has noted, I can add that a 1.12 generated world, updated to 1.13.2 and then opened in 19w02a, exhibits the same behaviour where the 1.12 generated terrain was unexplored in 1.13.2.

It seems that 1.12.2 generated terrain that is re-visited in 1.13.2 remains unchanged in 19w02a, but exploring outside of this causes world regeneration, leaving only blocks placed in what was minecraft:air in 1.12, to be left intact.

Confirmed for zombies and skeletons for me since 0.12.1 on iOS. Both drowning and falling mobs no longer drop expected items, except for armour. Also, burning undead mobs no longer drop items either when exposed to sunlight.