I'm using the latest version of Linux Lite, 4.46, just upgraded to that yesterday wondering if it would fix the problem. I'm using Xfce and it was installed along with the distro. I did not install it separately. I did play with appearances in settings: desktop, appearances, and windows manager.
I just did some searching, and although I can't find anything on my system (may need help to track it down), a google search says I received this theme by installing Linux Mint. Hmmm, that may mean I'm in the wrong place with this question.