I've had a couple of flare-ups of posterior tibial tendinitis (including one last week) - worth looking up for anything that feels like the achilles as the pain can radiate around the heel. I'm getting much better at a) recognising it and b) dealing with it. It's basically instant cessation of...
Have a look at these....was the source of years of calf and hammy tightness/tears for me. Solved with 2 mins of 'flossing' a day.
https://www.bettermovement.org/blog/2012/hamstring-strain-adverse-neural-tension
https://youtu.be/zzcncRdkHno