Are both versions of the iOS app (the one that works, and the one that crashes) on the same version of the OutSystems platform, and compiled using the same version of MABS?
Are there any other differences between the two that might be relevant?
Assuming the platform and MABS versions are the same, the next step I would recommend is creating a fresh app that is stripped down to just the essentials to test the barcode plugin, and see if you can get that working. If so, you'll need to ensure that the barcode plugin in the crashing app is configured the same and using the same parameters, etc.