First, if possible, I would remove the banner from one of the Adtan devices and then try to see if that works. Then we know it's the banner, and not the device template. If that fixes the issue, then I would modify the device template to work with your banner.
Are you using "Auto Determine" for device template? If you are, you may want to check to see if there is an Adtan template for the model device you have. If worse comes to worse, you can always modify the existing template or create a new one that works with the device.