System Information
Operating system: Window 10 home x64
Graphics card: 1GB GeForce GTX 760

Blender Version
2.80 beta
Worked: (optional)

Short description of error
Rigging Armature bones with constrain for twist control. At 180 rotation of all the rig the inbetween bones do a weird snap

Exact steps for others to reproduce the error
What I am trying to do is create a spine for humanoid characters. Create an armature and create 4 bones for spine chain and create two control bones to control the entire spine bone chain. Create constrain on the spine chain from the control bones so you can twist the entire chain using these two bones. Select both of the control bones and try to rotate it full 180 and you will see a weird snap in the spine bones chain. I am uploading a file so you don't get confused. (as simple as possible).