This is something that happens now and then mostly with the L shoulder button than the R (i suppose that it is due to usage). What happens is that the L button still clicks but the game does not notice the button press.

The problem is dust particles that managed to get under the shoulder button.
The way to fix is (i know this will sound weird but it works) put your lips around the shoulder button and blow hard, like you like it.
The shoulder button should be working now, if ever it is still not working you could try to use some "air in a can" to blow the dust away. If even this does not work your only option left is to disassemble it and clean it up manually.

Final warning though, it might break your DS if you go full out French kiss on it so just blow.

Man, these forums is gettin' racy today!!!

Yikes! Thanks for the tips, but could we get a bit more explicit? ;)

That's interesting, I noticed this when I was playing TWEWY.

This is very helpful!

This has been happening to me way too many times.

... why not just use canned air?

So i was searching up on google on ways to fix my shoulder button. Q-tip, canned air, nothing worked.

I was laughing out loud when i used your method as a last desperate attempt and it worked.

You rock Endogene.

"So i was searching up on google on ways to fix my shoulder button. Q-tip, canned air, nothing worked.I was laughing out loud when i used your method as a last desperate attempt and it worked. You rock Endogene."

Never had this problem so far, but if I ever do I will be looking at my GF to help me out after reading this.

how the frick does this work and why am i commenting on this in 2017??