Have you been using something like “The Stick” or a foam roller on the peroneals?
Mine are really tight when I do a sitting figure 4 stretch. I’ve told my PT and Dr. about this, and that’s all that they recommended.
I just got screened by a new PT and he ran a Fibroblaster tool over the area. It lit up with red blotches all over the place. He said those were lesions between the fascia and the muscle that were restricting movement and getting in the way of the sliding surfaces.