Plugin manager has been behaving erratically on my new Windows installation. I just installed XD a couple of days ago and haven't used it much, except to install and test out a variety of plugins. Sometimes plugin manager works just fine, but half the time or more, it just doesn't load entirely or takes a very long time to load. When this happens, the UI usually doesn't work. See the videos below for examples.
FYI, after recording the first video (the shorter one), I restarted XD, and then immediately recorded the second video.