Thank you so much. After testing the same section in slow-mo, it turns out that this may not be an issue of reaction times.
spoilers
https://i.imgur.com/AG9sypj.png
Here’s a screenshot of the section I’m talking about - the two circled parts have <10% of triggering. In both cases I’m holding ‘up’ while passing through them. Every other square has a 100% success rate so there’s something I’m misunderstanding. I’ll keep trying and switch back to the normal speed when I figure out why.
more spoilers
Here’s the path I’m taking if you want to double-check