I\'ve just received this message from Google Play but I\'m not collecting the Advertising ID.
Reason for warning: Violation of Usage of Android Advert
You are using crashlytics below 2.9.3. Apparently it's collecting and sending the google advertising id as a key in their header. That might be the or one of the issues. You can check if it's sending the advertising id through a proxy like Charles.
Edit ***
It seems that version 2.9.3 and above are still getting the advertisingID from by calling AdvertisingIdClient.getAdvertisingIdInfo() from the com.google.android.gms.ads.identifier package. I checked it by setting a break point on the method. I am assuming it is somehow still being send to fabric. Which would mean updating to higher version will not solve it..