Can't create new art brush, panel always tries to use the same incorrect shape

My "create brush" is absolutely stuck on an old shape. It comes up as this same weird stroke every time I try to create a new brush no matter what object I'm trying to use for it. Here I'm trying to make a frog-leg stroke (been trying for 3 days) and the same wrong shape comes up even when I try to create a brush out of a square shape.