Good morning…That is odd, but I’m wondering if there is a plugin conflict. Try disabling all plugins if you can, then try it out. Also, if you can, with the Seasonal Pro activated, are you able to go to the Customizer? If so, go to Appearance >> Customize >> Other Options, and disable the preloader and see if that helps?
Quick Follow up…I just activated my Seasonal Pro, and sure enough, it does the same thing. So disabling the preloader seems to fix it. This means there is something about the preloader script that is causing the problem.
Nothing to worry about. What I will do though is look into a fix for the next theme update (which is coming soon). You can leave it off as many often do. It’s basically an animated placeholder for someone to look at until the page loads up.