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The initial failure was most likely caused by dust! However, the subsequent failures were most likely related to defective parts, The new more robust latch that is intended to resist dust contamination failures is most likely related to a bad batch of new latches. fortunately the latch should still be covered under under a service parts warranty! I have attached a techincal service bulletin below relating to the dust contamination in the latch.
2003 Jetta left rear window blue plastic part of the