The banding is caused by differences in exposure across frames. You have several options to address the problem.

• Use the same exposure settings for every image. Manually set aperture, ISO, and shutter speed.

  If there is a huge variation of brightness levels across the scene, you can take bracketed exposures and process as HDR prior to stitching, as long as the exposure and processing is the same for every frame.

• Edit the images prior to stitching to match images to each other. This is probably the "easiest" to do with your current images, but it is time consuming.

• Use a program that can automatically correct for small differences between frames. Hugin uses one called enblend. The major hurdle is learning to use a different program. It's not as automated as Photoshop. (This is what I would do.)

• Edit images after stitching. Older versions of Photoshop were able to put images on separate layers after processing for stitching. I don't know if current versions have retained the ability. This feature was useful for correcting parallax errors.

I use auto exposure on my camera if the dynamic range of the scene is within Hugin's ability to correct it automatically. If dynamic range is greater than Hugin can handle, I attempt to adjust the composition. If that doesn't fix the problem, I don't bother taking the photos because it will be time consuming to process with results that are likely to be poor.

Based on what I can see from your sample image, it does appear to be salvageable. I would use Hugin, but you may be more comfortable manually editing the images in Photoshop so that the seams will match more closely. With so many images, it will be time consuming. You can reduce the work by removing unnecessary images and images that obviously don't match the others. You can try using gradient masks to change the brightness across an image to match different exposures in adjacent images.