System Information
Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.86

Blender Version
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-24 12:32, hash: rBbfe580642f46
Worked: (optional)

Short description of error
sometimes IK doesn't deform the mesh,

(After reparenting to armature, problem solved but if mesh was complex and weight painted, I was screwd up)
when I press R-click to cancel the transformation, constrained rigs don't Update,
while using copy rotation constraints and offset enabled armature shows jaggy shapes.

Exact steps for others to reproduce the error
[Please describe the exact steps needed to reproduce the issue]
[Based on the default startup or an attached .blend file (as simple as possible)]