For the Value Line shade (Grand Design Part #691416) in your 2020 Imagine TT that won't hold the lower position, the issue likely involves the spring mechanism becoming loose or misaligned. Begin by carefully inspecting the spring side assembly for any loose screws, broken components, or misalignment. Ensure that the roller tube is properly seated and the shade fabric is evenly wound. Adjusting the tension may help, but if the spring assembly is worn or damaged, replacing the spring might be necessary. If you are comfortable, remove the spring side to check for internal wear or damage. For replacement parts or further assistance, Elkhart RV Parts offers a variety of shade and blind components compatible with your model, and their experts can guide you in selecting the correct spring or repair kit.