Spike/hitch when connecting any node in Blueprint Editor

An odd editor bug started happening suddenly here. Whenever I connect any node in any blueprint, I get a 3-second editor freeze. EXCEPT for the first ~5 nodes I connect after restarting the editor. I did a profiling and the spikes happen on RenderThread → SlateDrawWindowsCommand → EndDrawingViewport_Dispatch → All command list execute → After Occlusion Readback → Present Time → Self. Any idea why this is happening, and how to fix it?

Figured it out. I updated my video drivers (NVidia), but my monitor started blinking (turn off and on again) too often, I suspected that was due to GSync so I disabled it.

Back to Unreal, the hitch is gone.

So the culprit was either outdated NVidia drivers, or GSync.

My monitor’s refresh is 240 Hz, if that helps any.