I’ve also had a similar issue.
Try this and please respond with your results.
Get behind a table, chair, pole, etc, that you can hold. Now take one leg and while maintaining foot contact with your entire foot to the floor, apply external rotation to your leg. I will usually feel tension in 2 areas. 1 – the big toe, and thus through the foot, which is optimally felt when you think about screwing your feet into the ground. 2 – the knee.
Now don’t over torque your leg. Just enough to put tension on your tissues. While keeping this tension, descend while keeping your knee behind your toes. Sort of like a squat, except this is more ROM type work, so you can support your body weight with your other leg and brace yourself by holding onto the chair, table, pole in front of you. Get your butt all the way to your ankle. Pressure should still be kept.
The key here is in order to maintain the arch, you should maintain the tension in your big toe. Now that you’re at the bottom, push your big toe hard into the ground while screwing your foot, and rise. Hopefully you’ve been able to keep your arch through this entire movement by keeping tension throughout the entire leg and foot.
Now the key for me to maintain my arch has been to focus on the tissues that have tension through this movement. I’ve discovered that I never really used my big toes before. I’m also realized that I never used my popliteus as much as I should. Lastly, my inner thigh muscles finish the connection of this movement with my hips and torso. If you can focus on repeating this motion, and strengthening the muscles you feel are weak – you should be able to start maintaining an arch.
For me it’s weird because I now understand the concept of torque in the body and how it creates the arch – but it’s hard to think that as I move (generally) forward through the world, that I have to create a rotation in my legs. Additionally, I have to create this rotation almost the instant I land on that foot. Previously, my muscles felt too weak to do this, and that I might tear something if I tried during a run or anything more than a controlled walk.
Now I can do so during walking and running, but still have issues during jump takeoff and landing.
Let me know if this helps! 😀