First of all, I don't know if this is REALLY really reliable (A.K.A. that does work to have it fixed forever), but as far as I have tested it, it does work way more time than when I tried the classic "blowing" method. As I have no idea how to disassemble my NDSL, I did try recently using a thin stick to get the dirt off the gaps in the shoulder buttons of my NDSL, which had a unresponsive shoulder button problem...and it seems to work fully responsively and constantly! Simply grab a thin stick or something thin to clean the shoulder button gaps. I used one of these: https://http2.mlstatic.com/palitos-de-altura-30-cm-D_NQ_NP_767305-MLV20847375612_082016-F.jpg Then use the thin stick, and keep brushing the gaps off for a while, and then check if it's now working. I can confirm for myself (at least) that it does give a good fix to the shoulders! Just was trying with Mario Kart DS, and works pretty well. Hopefully this gets work for everyone else!