Debug version ok Release version crashes

Cocos2dx 3.17 C++, Android
The release version crashes on launch with the following trace:
(debug version runs fine)

java.lang.ClassNotFoundException: Didn’t find class “org.cocos2dx.lib.Cocos2dxDownloader” on path: DexPathList[[zip file “/data/app/net.ttapp.rummyxhd-_FOWV4uuHDM1dXD-xnoikg==/base.apk”],nativeLibraryDirectories=[/data/app/net.ttapp.rummyxhd-_FOWV4uuHDM1dXD-xnoikg==/lib/arm, /data/app/net.ttapp.rummyxhd-_FOWV4uuHDM1dXD-xnoikg==/base.apk!/lib/armeabi-v7a, /system/lib]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:134)
at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
at org.cocos2dx.lib.Cocos2dxRenderer.nativeInit(Native Method)
at org.cocos2dx.lib.Cocos2dxRenderer.onSurfaceCreated(Unknown Source:4)
at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1539)
at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1270)