Amazon rejected my app because of "Duplicate files at the same path inside the APK"

I have an app already approved in Apple's App Store and uploaded in Google's Play Store (both current versions).

An old version of my app is also already approved into the Amazon Appstore. But now I've tried to submit the current version of my app, and they rejected it with this message:

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We are getting a publishing error from the Android SDK. It is finding duplicate files in the apk.

Kindly see if the Android is not happy with the apk by running this command:
java -classpath <path-to-android-sdk>/tools/lib/sdklib.jar com.android.sdklib.build.ApkBuilderMain <output.apk> -v -u -z [developer apk file]

When you run that command with the developer's apk, you will see:
"com.android.sdklib.build.DuplicateFileException: Duplicate files at the same path inside the APK"
which is the exception that breaks the publish.

Recommendation- Please fix the apk so they no longer see the error and resubmit the apk to the developer portal.

Please correct the issue(s) we found with your app submission.

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I've tried to run the command they suggest and I get the following:

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Packaging output.apk

myapp.apk:

=> assets/META-INF/AIR/application.xml

=> res/drawable-ldpi/icon.png

=> res/drawable-mdpi/icon.png

=> res/drawable-hdpi/icon.png

=> res/drawable-xhdpi/icon.png

=> res/drawable-xhdpi/icon.png

com.android.sdklib.build.DuplicateFileException: Duplicate files at the same path inside the APK

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In my ADT command line I don't specify any duplicate icon. This is my command line:

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adt -package -target apk-captive-runtime -storetype pkcs12 -keystore ..\cert\android.p12 -storepass xxxx myapp.apk myapp-app.xml -C . myapp.swf icons\myapp_icon_72.png icons\myapp_icon_48.png icons\myapp_icon_36.png

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Nothing out of the ordinary, as you can see. So, why is this happening? I also used the above ADT line for previous versions, and they approved them. The app is working correctly in my Android devices, so why are the Amazon reviewers concerned with that error message that only appears when running that command line they suggest? What's causing this? Maybe it's something that only happens in the latest versions of AIR (I'm using AIR 3.7).

Any way to fix this?

Thank you!