Had this same issue on my '09 Z - was in a terrible storm and had wipers going at max, and all of a sudden the left one stopped working. Barely got home and ended up fixing it by tightening the bolt.
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 '12 370Z + Sport | Stillen Gen3 Intakes | Stillen UD Pulley | Motordyne M370 | FI Exhaust | FI HFCs | 4.08 Gears | Uprev tuned
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