Returning intent always received as resultCode 0 and Intent data is null

Question

I have two apps that I trying to get to talk to each other. App 1 is an old app coded in Java in Android Studio App 2 has been written in Xamarin.Forms but currently only coded for Android

App 1 contains information that it is trying to change with information from App 2. App 1 calls app 2 via the following function:

private void launchApp(String packageName) {
    
    Intent launchIntent = getPackageManager().getLaunchIntentForPackage(packageName);
    
    String locationID = mCurrentJob.locationDetailDto.location;
    String taskID = String.valueOf(mCurrentJob.id);
    String userID = String.valueOf(Global.myUser.id);
    String deviceID = Urls.DEVICE_ID;

    if (launchIntent != null) {
        try {
            launchIntent.setAction(Intent.ACTION_SEND_MULTIPLE);
            launchIntent.putExtra("LocationID", locationID);
            launchIntent.putExtra("TaskID", taskID);
            launchIntent.putExtra("UserID", userID);
            launchIntent.putExtra("DeviceID", deviceID);
            launchIntent.setFlags(0);
            launchIntent.setType("text/plain");
            startActivityForResult(launchIntent, LAUNCH_APP);
        } catch (ActivityNotFoundException error) {
            TelemetryLog.error(TAG, Statics.ERROR_MESSAGE_TRY_CATCH_BLOCK + error, error);
        }
    } else {
        TelemetryLog.debug(TAG, "[launchApp][Error]");
    }
}

Here is the Receiver code in the same file/activity:

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // COMPLETION ACTIVITY
    
    if (resultCode == RESULT_OK) {
        switch (requestCode) {
            case LAUNCH_APP:
                String intentAssetID = Util.clean(data.getStringExtra("ID"));
                String intentAssetDescription = Util.clean(data.getStringExtra("Description"));
                String assetBarCode = Util.clean(data.getStringExtra("Barcode"));
                String assetNumberRef = Util.clean(data.getStringExtra("AssetNumber"));
                TelemetryLog.debug(TAG, "[onActivityResult]" + intentAssetID);
                TelemetryLog.debug(TAG, "[onActivityResult]" + intentAssetDescription);
                //If there is not (id + desc) and no barcode and no assetNumberRef
                if ((TextUtils.isEmpty(intentAssetID) || TextUtils.isEmpty(intentAssetDescription)) && TextUtils.isEmpty(assetBarCode) && TextUtils.isEmpty(assetNumberRef)) {
                    Toast.makeText(mContext, mContext.getString(R.string.completion_activity_no_asset_from_app), Toast.LENGTH_LONG).show();
                } else if (isPlanned) {
                    Toast.makeText(mContext, "Asset cannot be changes on a PPM job.", Toast.LENGTH_LONG).show();
                } else {
                    try {
                        if (!TextUtils.isEmpty(intentAssetID)) {
                            long id = Long.parseLong(intentAssetID);
                            mAssetUpdateRequired = true;
                            mNewAssetId = id;
                            mNewAssetDesc = intentAssetDescription;
                            showFieldsForNewAsset();
                        } else {
                            //The Asset app did not return an asset ID - it may have returned a barcode or reference
                            if (!TextUtils.isEmpty(assetBarCode)) {
                                mAssetUpdateRequired = true;
                                mNewAssetId = -1;
                                mAssetBarCode = assetBarCode;
                                mNewAssetDesc = "Barcode: " + assetBarCode; //Use asset barcode for displayed description
                                showFieldsForNewAsset();
                            } else if (!TextUtils.isEmpty(assetNumberRef)) {
                                mAssetUpdateRequired = true;
                                mNewAssetId = -1;
                                mAssetNumRef = assetNumberRef;
                                mNewAssetDesc = "Asset Number: " + assetNumberRef; //Use asset number ref for displayed description
                                showFieldsForNewAsset();
                            }
                        }
                        
                    } catch (Exception e) {
                        Toast.makeText(mContext, mContext.getString(R.string.completion_activity_no_asset_from_app), Toast.LENGTH_LONG).show();
                        TelemetryLog.error(TAG, "[onActivityResult][LAUNCH_APP] " + Statics.ERROR_MESSAGE_TRY_CATCH_BLOCK + e, e);
                    }
                }
                break;
            default:
                super.onActivityResult(requestCode, resultCode, data);
                break;
        }
    }
}

On App 2 the information is received correctly, a list of options is available, one is selected and upon button pressed, the selected item is converted into the required formatted model. I then use MessagingCenter to pass it from the Forms side to the Android side and this is where it is received and calls back to App 1:

protected override void OnStart()
    {
        base.OnStart();
        // App should return here after Submitting an Asset from the DetailsPage
        Xamarin.Forms.MessagingCenter.Subscribe<DetailsPage, SendAsset>(this, "Asset", (sender, arg) =>
        {
            SendAsset asset = arg;
            if (asset != null)
            {
                ReturnToCaller(asset);
            }
        });
    }

public void ReturnToCaller(SendAsset assetDetails)
    {
        Intent returnAsset = new Intent(Intent.ActionSend);

        returnAsset.PutExtra("ID", assetDetails.ID);
        returnAsset.PutExtra("AssetNumber", assetDetails.Code);
        returnAsset.PutExtra("Description", assetDetails.Description);
        returnAsset.PutExtra("Barcode", assetDetails.Barcode);
        returnAsset.PutExtra("Serial", assetDetails.Serial);
        SetResult(Result.Ok, returnAsset);
        Finish();
    }

Now, all this code works fine up until it hits the 'onActivityResult' on App 1. I have debugged through these steps tweaking multiple parts of the intent on both ends (eg removing flags, removing type, specifying type) and I can see that the return intent is as intended. It is populated with the Extras and is marked with ReultCode.OK (-1) but every single time it gets to App 1 the resultCode is always 0 with a matching requestCode to when App 2 is called.

Have I missed something obvious? Or is there some deeper routed problem? Any suggestion are very appreciated as I'm very stuck on this, thanks in advance.

Note: I have cleaned up the code to fit in here and removed the pieces that are not relevant or just plain commented out and changed some naes so that the code remains anonymous.

Update: So I am still having some troubles with this, but I have found that the reason I was always receiveing resultCode 0 and NULL intent data was because I was calling the SetResult and Finish from MainActivity instead of the SplashScreen which is set as the MainLauncher for the app. Now it will return a proper result but only when called during the processing of the SplashScreen. If I try to use MessagingCenter to subscribe to the response from the Forms page where I get the details, the message is received twice and doesn't close down the app (therefore not returning to App 1 at all)

I am trying to find the right way to Subscribe to this MessagingCenter but it seems that no matter where I put the Subscribe and Unsubscribe in the apps lifecycle, it will either call twice or not at all.