Transport Canada places the blame on a "build-up" of tolerance in the secondary catch mechanism, more commonly known as that handle you have to feel around for under the leading edge of the hood after you've pulled the release lever inside the car. That secondary catch is aptly named, as it's there to "catch" the hood if the primary latch fails while the car is being driven.
Should the main latch fail while the car is at speed and the secondary catch is faulty, the hood could fly open, with predictable results: a big shock for the driver, a sudden loss of visibility and the very real possibility of a crash. Hyundai says its dealers will replace the secondary hood catch with a revised part. The manufacturer also says the Tucson displays a warning in the instrument cluster when the primary hood latch is disengaged, and in Limited and Ultimate trims, that visual warning is accompanied by an audible one.