Rotation between spline points, only roll works!

I’m trying to use splines with an object that is rotating along the spline.

Setting the rotation points works, I checked all the points at runtime and they all have the right rotations.

However, when I try to move an object along this rotation based on time, it only takes the roll. I tried it both in blueprints and in C++, the roll works, but pitch and yaw stay at 0.

Could it be because of the rotator → quaternion → rotator conversions? Is this desired behavior?

I’ve wasted so much time on this that I almost used 3 splines with the different rotation axes of what I need as roll… Horrible!