The problem with hybrids is the fact that sometimes the teal family make nothing like their parents. The BWT and GWT look like (or resemble) a Baikal teal. Then take the gadwall which genetically speaking is related to several teal species, and because of that, when you start crossing certain species, you get birds that start to look like some of their old genetically related cousins.
The Labrador duck is an example of an idea that isn't too far fetched, even if it is only speculation. I believe we probably have many populations of birds that long ago were once parented from two different species, and then formed their own wild population.
Because the gadwall influences so many traits in birds, and doesn't really look gadwall, your bird could be anything. Is there a chance that this particular bird could be a hybrid's hybrid? In other words a hybrid that bred to a third party that wasn't part of the original (two-party) strain?
It has many characteristics that could be a few ducks in my opinion. Wing looks GWT or pintail (I don't know the size of the bird). The head and throat patch again could be pintail (throat) and GWT (green stripe). The tertials look longer than usual, and resemble falcated, but probably not? I guess pintail GWT or possible hybridized version of that, if there was a possible third party involved....but if you don't know, I CERTAINLY don't know.