Hello. My name is***** can assist you with your question.
This usually means that the tension is not even on the rollers. On this particular model, it is easy to make the adjustments to straighten out the roller. I am going to upload the manual here for you. On page 16 there are specific instructions for doing this. It includes diagrams as well. But if you have any questions about it, please let me know and I will help you until it's done.