You can’t just add anything to the Android res folder. There is a very strict structure for the things that go into the res folder:
Note that there is android/res/raw which is for raw data of any format. But loading from the res/raw folder requires the use of the Android API function Resources.openRawResource() so that’s not going to help you.
The instructions for defold-fmod specify that the banks should be put in android/assets/banks.
So move the banks to ROOT/bundle_resources/android/assets/banks and the bank files should end up in the assets folder of your APK.