if you look at the transform rotation of the y, it jumps from 221 to -139, when i’m moving the object locked along the z axis. i don’t understand how that makes any sense. literally, i don’t even have to move the object. if i just hit g, without even touching the mouse, the rotation goes to -139. how is that even possible? i’m not even rotating the object and it’s changing the rotation of the object.

in the first image you are not on the position of the keys, the transforms are green, in the second image there is a key on z-location and y-rotation.

i would look in the graph-editor, (zoom on the keys) to see whats wrong on frame ~1016 or ~1017.

It’s called “aliasing”.

So first, think about how if you rotate something 720 degrees, it’s the same as not rotating it at all. 720 degrees of rotation is the same as 360, same as 0, etc. Any number of values can all be mapped onto the exact same orientation.

3D Eulers alias in another way too. Think about if you wanted to describe the position of a person on the surface of the Earth, along with their heading-- an orientation, right? You might use 3 numbers. Say, heading, latitude, and longitude.

But wait-- latitude only goes to plus or minus 90 degrees, doesn’t it? Huh, you really only need 2.5 Euler angles to represent any particular orientation…

And if you think about rotating X, then Y, then Z-- what’s the difference between 180, 0, 0 and 0, 180, 180? Same orientation.

In order to use a consistent set of values, Eulers pass through a conversion, so that Blender can recognize orientations that are the same as the same, even though they use different numbers.