Most of our customers call us because they had enough of having to put the screen door back on the track after it fall off every time. When a sliding screen no longer slides good it might be time to replace it, or maybe have a screen company like mine that is mobile come out and give you a free estimate.
Most screens don’t have to be completely replaced, there are way to fix frames and rollers and the way they fit. You will save some money and if repairing is possible they will be just as good. If they are bent or missing then you will have to get a new screen slider made for the openning.