Hi
I have a client with similar problem. Try 2 things: 1st , if you or ask someone to stabilize your distal Tib-Fib jt , anteriorly and then try gently bring your calcaneus anteriorly (basically P>A, AS IF YOU ARE DOING ANT DRAWER Test) during that you can either do some active Dorsifexion or ask the 2nd person to do it passively for you.
2nd. Try or ask someone , to create some compression between distal Fibula and Tibia (Interosseous lig. instab.) and during that, again Passive or active Dorsiflexion.
Be very gentle and careful with all above.
Let me know how it goes