System Information
Operating system: Windows-10-10.0.17763-SP0 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 451.48
Blender Version
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-08-15 17:06, hash: rB2c61c3d733cf
Worked: 2.83
Short description of error
Add a cube, throw a sub-d modifier on it and try to move vertices in edit mode