Can you please indicate more about your input data. I see you mentioned 3 band, but not bit depth or anything else about the input rasters? Usually 3 band rasters are either 8 bit or 16 bit. Based on your experience, I am guessing that they are 16 bit, because they are usually usually the more problematic. Can you indicate if the issue is with 16 bit inputs or 8 bit? Also can you indicate what bit depth you are setting on the input raster? I tested here with some imgs that I had that were 8 bit and they are fine.