I would assume it's a hardware issue. I know on the Tjets, they had a strip of white vinyl on the side. If that got bunched up or wrinkled, etc., it could cause something like this. I'm not sure if the Kiosks had this strip or not. You may also want to check your encoder strip with a flashlight and see if there are any marks or ink on the strip. If so, clean it very well with rubbing alcohol or windex.