% of API Calls in v2.x stuck

We updated the facebook sdk on Android as well as Django Backend(using facebook-sdk) to latest almost a month back. Facebook still complains that 19% of api calls are still made from V1 graph api. Only reason I could think of is from users who have not updated the app. But this figure is stuck on exactly 81% from past 2 weeks. Is there anything that I am missisng. Any help would be appreciated.