I have always worked with plastic Paterson tank and reels for processing the film in both 35 mm and 120. Recently, when I was developing two 120 films, a straight line parallel to the border film appeared in one of them. As I think it could be a mechanical problem with one of the plastic reels, I have decided to buy new reels and replace the older. However, it could also be the opportunity to change to Stainless Steel Tank and Reels. I would like to know your opinion. Additionally, I ask you to recommend me what stainless steel system to buy and, if possible, the internet link to the on line store. Thanks for your help, Henry.