We have had a number of reports of an unresponsive GUI from macOS users that also have a "window manager" app installed, such as Moom or Magnet. With Moom, disabling the Move & Zoom when dragging a window to a display edge or corner feature resolved the issue. For Magnet, we have not yet pinpointed exactly which feature is causing this so disabling the app is the only known work-around at this point.
We will keep an eye on this and update when we know more.
Update: The latest Magnet version fixes the previously broken Ignore DbVisualizer functionality. Ignoring the DbVisualizer app will prevent it from being sluggish while Magnet is active. The side effect is however that Magnet will not work for DbVisualizer.