I believe there are something wrong with your theme. But I can't go through every single element of it and pin point where is the problem. I did also saw a few other odd behavior in your theme.
For me, usually this happen when building a theme from a problematic/not compatible old windows theme. And the problem will be carried forward/inharit when you build a new theme on-top of old one. My suggestion is to build this theme again, using a known good windows 10 good theme. Replacing all the graphics and setting with your own.
Just my opinion. Others might come along and give their expert input
Thank you,
Basj,
Stardock Community Assistant