System Information
Operating system: Linux Mint 19 Tara
Graphics card: Nvidia GeForce GT 630

Blender Version
Broken:
2.80 (sub 35), branch: blender2.8, commit date: 2018-12-01 23:15, hash: 8c620c8e2b3, type: Release

Short description of error
Displacement texture doesn't refresh the result automatically

Exact steps for others to reproduce the error

Try to change the texture settings. You will have to go back to the modifier tab, tick something inside the displ. mod. field in order to make blender update your texture.