GIMP :: Color After Bucket Fill Is Not Solid / Some Pixels Remain Translucent

step 1) I remove the background of my image with the color to alpha method, isolating the part of the image i want.

step 2) I then use color select tool to select all the transparent area that was left behind from step 1.

step 3) I create a new layer.

step 4) Then I use the bucket fill tool to fill in the area on the 2nd layer that was selected in step 2.

This is where I run into trouble. On some pixels where the color filling meets dotted line area (made by color select tool) the color comes out translucent. I don't want this to happen. I want it to be solid ff00ff (color hex) without the random reductions in opacity.

I'm working with sprites and the emulator i use has ff00ff as transparent. I'm getting random pink color coming out of the edges of my sprites. These little specks of pink should not be appearing in game because it is supposed to be read as transparent. i suspect that these specks coming out are related to these translucent hiccups made in gimp.