We’ve had a few other reports of this happening during loading screens, so it is something that we’re tracking. Unfortunately it is not clear what the cause is at the moment, but there are a few workarounds that you can try.
Try disabling G-Sync (in the Nvidia control Panel) or Freesync (in the AMD Radeon Settings) if your monitor supports either of those technologies.
Try switching to windowed mode to see if the issue persists. This can be done in-game by hitting Esc -> System -> Graphics and changing the display mode to windowed.