All our electronics (excluding sound) worked on the first try and we did not have to keep reassembling the components. Small win for us. We figured out it was likely connection issues which caused the inconsistent results, and hence considered soldering the components on the breadboard. 

In our next check-in session, Dr Ho and Hanyang suggested we use high frame rate on our phones to calculate the precise speed of the launcher, and add weights to our foam balls. The nerf gun idea was brought up again, hence we decided to visit the nearest place to get a nerf gun directly as we did not want to wait for the online purchase to arrive. Hence we went to Kiddy Palace. Where we were totally not judged by the cashier for getting the nerf gun rated 14+.