Whats wrong with my achilles !!?

well august this year i broke both tibia and fibula and i have had an amazing recovery as my physio says im only 1 month into physio and its like i have done 7 months, i can play non contact football, balance on a wobble board stand on each foot and hop, but most recently while eating lunch and playing badminton i collapsed due to my achilles giving way, it hasn't snapped, and i am flat footed meaning i have a very short achilles but i suddenly feel a twinge then it just gives way, whats happening ?