Hi, I have the same problem, If I right click on the editor the frames will go crazy then If I right click outside unreal all go back to normal.
I’m also running a GTX 1080 on a i7 6700k and this is UE 4.18.2 with a new “Third Person Project”
I don’t have this problem on a similiar machine with a GTX 1070 and i7 6700 ( not K version )