Remove motion blur from certain consistent areas of video

I realize that I'm asking something that has been technically answered here (removing motion blur from certain areas — FXhome Community), but I didn't want to push a 2 year old thread since some people have issues with that.

I understand and have followed all the steps to achieve removing motion blur from some areas, but for some reason the masks I set to "subtract" just turn into black boxes, even after exporting. Changing each subtracted mask's feather to "In" and setting the feather length to "2000.00 px" removes the black box, but also allows the motion blur effect to stay in the masked areas.

I want to know how to make the subtracted masks visible as they appear throughout the entire video, except with no motion blur.

Picture included for reference and thanks in advance!