Has it happened to your other controllers too? So far I only have one controller it hasn't happened to, and it's third party. I refuse to pay $70 for the Pro controller if there's even a chance this could happen to that thing.
Yeah, it's the Pro controller alright. It's a relatively well known issue among the Splatoon community since that's the main competitive game where the Pro is the "standard" controller, but mine having to deal with Smash on top of that lead to the inevitable, really. It's not too bad, at least not yet - sometimes it drifts a little downwards and I just gotta blow some air into the thing to get it working again. But yeah, it is concerning.