I tried the test project and my editor runs fine now after a long time keeping an eye on it (5 mins atleast). I do however have a maybe related. In my game that ofc ran fine in 4.18, it now shows these rather periodic stutters. I checked GameThread and RenderThread, and they both run fine within the 10-11ms threshold for VR (Vive), so something else i causing these stutters. And note, this is running it Packaged, so its most probably not the same as the OP, but nevertheless may be related.