Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX TITAN X/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.30
Broken: version: 2.81 (sub 11), branch: master, commit date: 2019-09-15 18:34, hash: rBb043bef000e9
Short description of error
after sculpting for a couple of hours using dyntopo I then started making a material with cycles and ambient occlusion nodes and after creating about 20 nodes in the node tree I pressed ctrl z to go back one step blender skipped back to after just sculpting and my material disappeared with nothing happening when I try and redo.
Exact steps for others to reproduce the error
Sculpt using dyntopo with constant detail at about 40, back to layout tab, enable cycles, create environmetn texture with HDRI, create material and input 20 different nodes with ambient occlusion node. Then press Ctrl + z