I'm starting to believe there isn't anything wrong with the shifter. This is my first bike with a Heel/ Toe shifter. I've been watching it closely, as I realized after posting that I had never actually witnessed the shifter sticking, I was just assuming, since I would try to shift, and it would stay in the same gear.
After posting this, I decided to actually visually watch the shifter with each shift (as long as the situation was deemed safe to do so) and see if it's moving back to the rest position, or if it's sticking, as I believed.
I have yet to have it happen again. The shift lever springs back into the rest position after every shift.
I'm starting to wonder if it was all operator error. Maybe I was resting my heel somewhere that didn't allow the shifter to come back to the proper position after a shift, thus causing it to seem like it was sticking.
I'm going to continue to keep an eye on it, but it appears to be working perfectly.