I'm not sure what events exactly you used, but I assume you made it add when the player collides with the coin. Try the inverse, add 1 to the private variable when the coin collides with the player...
Hmm... You were right, I did indeed have the player colliding with the coin, but when I switched it around it didn't fix the problem. However, when I combined it with Guyon's tip:
My thought is change to over lap. Try that that instead of collision.
...It fixed the problem entirely. I ran multiple tests to see if it had truly fixed it, and it did. Thanks, guys!