fallwatcher

I encountered the same bug today. I started a new world, and when I saved and closed the world, then opened it again to continue playing, every block I had placed in the world had disappeared. Every dirt block, hay block, berry bush, basket, etc. vanished. However, all my character's inventory items were still there. Recreated the world with the same seed and settings, and in this world, everything I had placed vanished after I went several hundred blocks away from spawn and then returned to spawn. Started third world, using the same seed, and this world generated completely different from the first two world,s which was surprising, but this new world has not yet exhibited the "vanishing blocks" bug. I should add that I only play vanilla. Additional information: I've been playing Vintage Story for over year, and all my old worlds still work fine. The problem began with the first new world that I generated with 1.12.6. this world was randomly generated. I exited the game, after playing for about 1.5 hours, with the leave world button. When I came back to the world, the terrain appeared to have reverted to its original state except that there was no tall grass in the areas I had build in. Nothing I had built was there. I then created a new world using the seed copied from the first world. In this world, I got the bug without exiting the world. Instead, I walked several hundred blocks away from the spawn area, and when I returned, the spawn area had again reverted to its original state, except the tall grass was absent in the areas I had built on. I didn't use the prospecting pick in either world. In both worlds, I customized the world size, increasing from the default 1 million block size to 2 million blocks, but I left world height at the default 256 blocks. Finally, I randomly generated a third world, but did not make any changes to the world size parameters, and that world is fine so far...