Faulty screen door latch

My latch keeps sliding down when I close the door, causing it to lock me outside. There is no slider on the exterior part so I can undo it. The door doesn't show a brand name but came from Lowe's, installed on a Pella sliding door. The only markings I see are a 5 on the interior part with the latch, a 2 on the other part. Has 3 screws. Thanks for any help with a replacement.