Black edges on build object cc (transparency issues?)

I used one of the paintings from the game to build this object. It doesn't have transparency built in so I followed this tutorial on applying alpha. After that, in S4S at least, the areas that I wanted to be transparent became transparent after following that tutorial.





But when I open it up in game, it has janky black edges like this.






I assume it has something to do with transparency, but since everything "looks" fine in S4S and blender, I'm lost as to where the source of the problem is.

Here are my .package file and blender file, if they might be of any use to diagnose this problem.

If anyone has time, please take a look, thank you!