If you're really worried about performance with A*, you should look into A* Jump Point Search before you go ballistic and divide the pathfinding into multiple sub-parts. But that's for later, right now you should focus on fixing your bug.

I didn't download your code, mainly because a) I don't like dealing with file hosting sites and b) if it's a whole project it probably isn't a short, self contained, correct example (which means there's a lot of stuff to wade through).

Like jefferytitan said, the "crinkle" is probably a bug. If you're using a heuristic that's greater than the actual cost, it's possible to for a non-optimal path to be found (although I think it'd have to be a pretty terrible heuristic to get a "crinkle" like that, so I'm leaning towards it being a bug; usually even the non-optimal path is pretty smooth/consistent). Try a) running the program in your debugger and perform an A* search by hand (where you're not just following your code) to see if you can find where the two deviate from each other and b) printing out more useful/readable information in your "map" (i.e. show scores, parents, etc) (you can change it to show parents one time, run it, then change it to show heuristic scores, run it, then change it to show actual scores, run it, etc to see how it's behaving) (be sure to run it in a step by step manner so you can watch it working, don't just run it and look at the final results).