I experienced this many, MANY times, mashing faster won't do much until a certain point since there will be a row of those blocks you're bumping into as well (like you can create a row of 8-9 of those note blocks). I'm not sure if tit's because you're getting too low where you're very close to hit the death barrier already, no idea if people discovered why this is a thing, something I'd still need to find out... xD