I don't see how a gasket would help. Loosening the screws to eliminating the binding and lubricating with a dry graphite spray should do the job. Do not use W-D40...it is NOT a lubricant. Graphite is the best for locks, clasps and hinges. Powdered graphite is good as well but would likely be messy for that latch. That's why the dry spay is best for that application.
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