The issue with your 2016 Tiffin Open Road 36LA roller shade not staying down and retracting slowly is typically caused by a worn or broken spring or an internal roller mechanism problem. Based on your shade width of 53.5 inches and the approximately 23-inch spring length, the most suitable replacement is the Irvine/Valu-Line 0.75" replacement spring in the long size (24" spring length) designed for shades over 40" wide. This spring restores the tension necessary for the shade to stay down and roll smoothly. Avoid forcing the shade assembly as the spring provides the needed tension to roll it back up. Additionally, if the end bracket or dial assembly (specifically the black Day/Nite end bracket) is damaged or the pin has broken off, replacing that bracket will also be necessary. You can find these parts and detailed options at Elkhart RV Parts to ensure proper fit and function.