I've been testing the world-gen/game-play/etc for the past few weeks, with a "modpack" that I'm in the process of putting together. The worlds will randomly fail to save properly, then they refuse to save any progress after reloading the game/save. There are no crash logs or errors.
I currently have;
Biomes o' plenty.
Platforms. (I'll be ditching this one anyways.)
Spice of life.
Storage drawers. (This one might go bye-bye too.)
Tough as nails.
Minecraft comes alive.