Appearing infinite Terrain in flat world

I have Created A Minecraft Server since A While And It Was Flat it was created Before Village And Pillage Update Was Released  So I Needed to Update it I followed That [Reddit Article|https://www.reddit.com/user/ProfessorValko/comments/9f438p/bedrock_dedicated_server_tutorial/] About BDS (Bedrock Dedicated Server) To Know How To Update After A While From Updating I Began To See An infinite Terrain Higher Than The Flat Layer There Was Mobs Spawning Everywhere (Mob Spawning Was Set To False) Even Water And Lava Physics Was Messed Up So They Don't Fall To The Flat Layers I can't Make A new Server I Have Built A lot In It So Please Mojang Fix This bug