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 442.19

Blender Version
Broken: version: 2.83 (sub 2), branch: master, commit date: 2020-02-01 16:56, hash: rBf051d47cdbce
Worked: (optional)

Short description of error
object normals not updating on undoing a linked object in sculpt mode

Exact steps for others to reproduce the error
make a sphere
shade smooth it
alt + d to duplicate a link of it (the important part!)
select one and go to sculpt mode
do a brush stroke on it. (do a harsh grab brush for example to make it more visible)
now ctrl+z undo it.
see that normals get stuck
after another brush stroke the normals get updated.

• the effect is more visable with a matcap

This bug is here even before 2.80 came as I remember.
Basically this happens with every smooth shaded object that has a linked object. Even if not smooth shaded it will appear even after doing the smooth shading last!