Operating system: Linux-4.15.0-74-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 390.116
Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-11-20 14:27, hash: rB26bd5ebd42e3
Short description of error
Trying to do a space switch on a rig using the 3D cursor I found it snaps to a wrong position.
The bone is constrained using an armature constraint, that is keyed on the weights for the space switching
I set up a simple file that reproduces that bug.
Incidentally I found, that using python to set the matrix of the bone has similar results.
Exact steps for others to reproduce the error
Download blend file
select constrained bone
shift+s selection to cursor
bone move up instead of down to cursor
Original blend file: