Can't pick up items in certain chunks

Dear Minecraft Mods,
I have a problem in my Minecraft world and when me and all my friends try mine some blocks in some chunks they just sit there and float and its wearied I dropped items in some chunks, and they just float and they can't be picked up I don't really know how to fix this myself, but I am trying my hardest. I thought it might be a command block issue but sadly not. I even god a coder who codes anti cheats for vanilla minecraft but still to no provable, I tried to reproduce it in a diffent world but nothing happens. it just seems to effect my SkyGen world but I can give you the world download if that is any help completely unmodified and command blocks off. its the best I can do. thought since you're the minecraft developers you can figure out what's going on so yeah. Any way is a world download good enough? Its the best I can do! Ummmm I Can't unload the video file because it says 10 mb only but I can however upload it to YT privately and then give you the link. Ok here is the link that will show you the bug: https://www.youtube.com/watch?v=Rr79xIVx8jE