You are required to hold space, but its not tied to animations.
once the bar drains completely you need to let go of space,
I'm unsure still, I am playing in a non-standard monitor
if framerate is related (very likely it is) that could be the issue, as if I start holding space any time before or after the prompt appears, it instantly fails
so many games have this issue with non 30FPS and 60FPS that causes QTEs to be unwinnable