My editor is stuttering a LOT now. The stat tools show it hopping from 12 ms to 40 every second or so. I think I’ve narrowed down the issue to being from the engine itself, having tried it in several projects. I am currently running a gtx1070, i7 6700k, and 16 gb ram. No other intensive process is open when I try this.
Have you upgraded your graphics drivers? If you did so recently and it started occurring after you did so, have you tried reverting?
Did you add anything into the project that started causing serious performance loss? You can use the command ProfileGPU to find anything thats seriously bogging down your card and the engine itself while its running.
Have you tried clicking on Settings (big button at the top of the editor) and then Engine Scalability Settings, and then clicking on a lower quality setting button there? Worth a shot - might help.
It can be NordVPN if you use that. In my case I have to be connected to a VPN or it behaves like you say.