Problems with restricted production FB app, but a duplicated FB app does work

Question

Recently Facebook started to review our App, which followed in a restriction because our app was violating the Platform Policies. Both our Android and iOS app had a bug. We already fixed that bug, but didn't push the update to the Play Store and the App Store. After Facebook notified us about the restriction we pushed the update into production and requested a new appeal. However, the appeal was declined because of the Android app which still had a bug.

I couldn't find a bug and because the app was restricted we couldn't really test it. If we'd login using Facebook, we got an error message from Facebook telling us that our app was restricted:

To debug the Facebook login process I created a new Facebook app and copied all settings from the restricted FB App to the new 'debug' App. After changing the API keys and doing some testing everything seemed to work perfectly fine, even when setting the app status to production in the FB App settings.

So we knew that FB was sending the Android app some error code. I created a small update where the App will shows a part from the message sent by FB. We created a new appeal. Unfortunately, the app appeal got decline again. This time the send us a print screen with the error message:

Not that much information, however, this is an error message returned from the Android FB SDK. I tried to search the error message on Google and the Facebook Docs. The only thing that I found was this Stack Overflow post. It has to do with test users, but our app is in production, so we should have to add test users in production.

I'm clueless about what to do or try. I tried to email FB, they replied and basically said that I should try and ask a question on Stack Overflow. Which obviously is what I'm doing right now. Has anyone every experience such problems or how would I test this in production?

Edit

The code where the error is caught. The LoginManager is from com.facebook.login.LoginManager

loginActivity = myActivityParent as LoginActivity
facebookCallbackManager = CallbackManager.Factory.create()

LoginManager.getInstance().registerCallback(facebookCallbackManager, object : FacebookCallback<LoginResult> {
    override fun onSuccess(result: LoginResult?) {
        Log.d("FACEBOOK", "Successful login.")
        loginPresenter!!.onSuccessfulFacebookLogin(result)
    }

    override fun onCancel() {
        Log.d("FACEBOOK", "Facebook login was cancelled!")
        enableViews()
    }

    override fun onError(error: FacebookException?) {
        val errorMessage = error!!.message.toString()

        displayErrorBoxTimed(errorMessage, myActivityParent, length = 5000)

        Log.d("FACEBOOK", "Something went wrong while logging in with facebook!")

        enableViews()
    }
})