SNES USB Controller's Buttons Working Sporadically - HELP!

I have just bought a used Retrolink usb snes controller and it doesn't seem to be working properly. I am wondering if the issue lies with the controller itself or, if not, is there anything I can do to fix this problem. I am running Windows 7 and it recognizes the controller when I plug it in. When I open up Nestopia and go to 'input' the controller shows up there as well. I am able to map out the controller's buttons the way I like and each button is recognized when I assign them. I then press 'ok' and attempt to play an NES game - this is where the problem begins.

When I press the buttons on the controller they will respond half of the time or they won't work at all. Sometimes when I press an arrow to make the character run it will keep running after I take my finger off of the arrow. I'm assuming that there is a problem with the controller itself but I'm quite inexperienced in this area so I'm really unsure.

I told the person I bought it from and they said it had been working fine for them up until I bought it. This seems to be an honest response from him. I will say that when he dropped the controller off it was raining quite heavily and it was exposed to the rain very briefly...

Can anyone offer any help or advice? I would appreciate any feedback.

Thanks.

never used it, and am no controller expert. but a simple way to figure it out... this goes for most issues not just controller related..

use multiple devices for process of elimination..
try ur game with the keyboard c if it responds correctly,
try a diff application/emu/game c if it responds correctly,
try the controller in a non shared diff usb port
try a diff computer if possible

if all but the controller respond correctly, would be safe to say its the controller.

tho not to jump to conclusion's but from ur last statment, sounds like the guy selling it was one of those bullsh1t forgein importers selling garbage, or something a kid low on 'meds' found to sell so he can afford his next high.

from my own experience and observation, not regarding controllers, just electronics or anything for that matter.. If u buy used, its most likely going to be beat to sh1t, u get what u pay for, but often less than what u pay for lol.. unless its one of those situations where someone passes away or a desperate garage sale, or u just get lucky.. In this case its just a controller so doesn't really matter, but depending were u live for important things i would advise never buy used, especially if the person selling has a big smile on there face or loves to talk even when u didnt ask them a question about it.

Controller issues are easy to figure out. First off stop testing it in the emulator as that is only going to complicate things.

After you plug it in, go to the game controller control panel and test it. short cut ( run joy.cpl ). If it works in here, its an emulator issue, if it does not its an adapter issue. The only way to know if the controller is any good, is to test on the console or buy a new one. %99 of the time its the cheap adapter that causes the issues. Retrolink is known to have issues.