Stick drift can be a real game killer... definitely sounds like the cause. Too much deadzone can also make a game unplayable. Good thinking...
A small story: I played a game on Wii U before that has the deadzone for walking set so high that if you were to play it with any 3rd party controller, it would not let you run at all or certain directions would have the same effect. It's like they made sure you had to use their brand of controller lol. That's kind of messed up... Making the game pretty much unplayable unless you had a brand new Nintendo controller. Xenosaga I believe it was. That's besides the point though. My point is as stated at the top. Analog sticks, especially worn ones can be a real pain sometimes.
I have to agree that adding a small analog stick dead-zone should definitely fix that problem. Very logical thinking for sure. Everyone makes mistakes indeed. In fact, I have another quote for such an instance that I added to...
"Learn from your own mistakes as well as the mistakes of others to be better where we can be."
And I would say you've done just that Ellise. ^_^ Good on you! Just trying to give praise where praise is due. Hope you don't mind. Have a Great Day!