Weird.
On the new Alpha build that dropped really recently.
I got to past the first area and went onto the jumppad. But my vine didn't follow and my sticks would only register down and not up. My little seed was shaking furiously as I couldn't help but move further and further away from him. Eventually, my seed dropped down to the previous level (where my vine was stuck, and I regained the ability to go upwards once the seed landed on my vine again.