System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.48

Blender Version
Broken: version: 2.90 (sub 0), branch: master, commit date: 2020-05-01 14:06, hash: rB60741cfe181c
Worked: (newest version of Blender that worked as expected)

Short description of error
In the new multires, if I sculpt on a level, then subdivide, sculpt on that layer again, then undo to the base level and redo back to the higher levels, it creates a pointy mess in the place of where I'd sculpted.

1. Remove default cube, add UV sphere. Go to sculpting workspace.
2. Add a multires modifier and create a few subdivision levels.
3. Sculpt on those levels and undo back to the lowest level.
4. Redo back to the higher levels. Some of those steps would have pointy shapes.