Is the tube seated properly inside the tire? Seeing its happening near the stem, the tube may not be fully inside the tire when you inflate it.
Deflate the tube then push on the stem as though you are pushing the stem out of the wheel and at the same time make sure that the tire stays seated on the wheel. If the stem pushes all the way to the tire then the tube is "seated" inside the tire. If it isn't that may be your problem.
Otherwise, I wouldn't know what is causing the "blow outs"