I had some experiences. First, you take the astray off, and check to see if anything's broken (if so and cannot be glued, get another one from ebay then). Otherwise, you play around the latch mechanism to have a good understanding as for how it stays closed. Next you will find that the reason it doesn't stay closed is because on its return path to the closed position, the guide pin doesn't follow the 'right track'. You then can place a piece of Velcro inside the track to aid the guide pin to its correct path. That solved my problem.
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