I also had this issue, but did not fall through the world.
Inside my home:
Eleanor’s Enchantment Shop:
Whittacker’s Crafting Shack:
System Info:
Windows 10 Home 64-bit
AMD Ryzen 7 3700X 8-Core Processor (16CPUs), ~3.6GHz
16GB RAM
DirectX 12
Nvidia GeForce RTX 2070 Super