Intermittent selection in viewport (all versions)

I am experiencing an issue whereby selection of BSP objects and actors is extremely intermittent, it’s taking between 2 and 20 clicks to select an object. All other UI outside the viewport responds fine, including selecting objects in the view outliner.

Been using UE4 at work and haven’t come across this issue before, mouse is responding correctly per click as the cursor blinks every click.

Using DX11, AMD RAdeon 5700 series card, latest drivers