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
Stardock Community Assistant