Pansharpening using the OTB Toolbox


I am trying to pansharpen some Landsat 8 imagery using the OTB Toolbox. Since the Pansharpening Methods do not work, I set up the BundleToPerfectSensor algorithm and tried to pansharpen a multispectral Landsat imagery. However, at the end I only get one band instead of the three input bands.
Does anybody have an idea why this happens or can give me some advice on how to pansharpen multiband spectral imagery in SNAP?