hello mojang i found a bug on my hardcore world I'm exited to the new update and now i found a bug i just update my old hardcore world and then suddenly other chunks did not load or missing

chunks missing 🥲 i just want the new spear but bugs on my world happened because on my old hardcore world can't craft a spear i i back up my world and deleted Minecraft and re install game then i import my world and the bugs happened the chunks missing sorry too my English I'm not good of it plss hear me up thank you🙂