Barcode-Scan with Front camera is not working

Hey there!
First, thank you for this project. It was really easy to integrate and works pretty well.
But now I wanted to use the front-camera to scan barcodes. So far so good, this also was pretty easy to activate.

The problem is, that I can't scan any barcode as the front camera mirrors the whole image as you might see on this photo:

I don't think that this is a configuration problem or something.
The back camera is working fine, as always.