System Information
Windows 10 Education - Version 1803 - OS Build: 17134.112
Graphics Card: EVGA GTX 1080 Gaming ACX 3.0

Blender Version
Broken: 2.79 (sub 3) hash: b5b5260, type: Release, branch: blender2.8

Short description of error
When using the mirror modifier, having an empty object as the mirror modifier target while the empty is parented to the object with the modifier, incorrect mirroring occurs randomly when the object is moved.

Exact steps for others to reproduce the error
Create a cube with radius 1.
Create a cylinder with radius 1 and depth 2 at the coordinates (0,0,2).
Create plain axes at coordinates (0,0,3).
Parent both cylinder and empty to cube.
Create mirror modifier with object target as the plain axes on both cube and cylinder. (This allows better gauging of misplacement)
Press G and wildly shake cube mostly along the z-axis.
While shaking randomly press left click to place cube.
Notice that sometimes the separation of the mirrored cube changes in the viewport, but is corrected when either

1. The mirror modifier on the cube is hid and unhid.
2. The following sequence is followed: Create an object -> Move newly created object and confirm location -> Press CTRL+Z to undo.
3. When rendering with Cycles.

I have attached a .blend file with the above set-up and a video illustrating the phenomenon.