System Information
Operating system: Windows-10-10.0.22000-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 472.12

Blender Version
Broken: version: 3.0.0 Beta, branch: master, commit date: 2021-11-03 21:09, hash: rB3e6907eb8a3d
Worked: 2.93.5

Short description of error
When deleting at least one vertex of a mesh with custom (split?) normals, the entire object develops artifacting. I'm not quite savvy about how normals work but I believe they're being removed entirely. I am also not sure if any other types of editing also affects the mesh in this way.

Exact steps for others to reproduce the error

1. In Blender, have a mesh with custom normals in the viewport. I provided both a sample .fbx and .blend file (initially saved in 2.93.5 to open in 3.0 and compare results) in this bug report to avoid any hassle.
2. In Edit Mode, select one vertex and delete it.
3. It can be seen that the entire mesh begins to glitch out.

Video (left is 2.93.5, right is 3.0)

Other files