Frame animation. when I alter an object in one frame it changes in every frame it appears in.

I am trying to make an ultimately simple animation in Photoshop 2023. This animation involves an oil pump. After the pump appears on the screen I want it to rotate up and down. I create the animation timeline, make the pump visible and then add about ten frames so the pump sits still on the screen for a time before it starts moving. Then, while the last frame in the animation is the only frame that is selected, I select the element that I want to start moving (a smart object imported from Illustrator 2023) and I rotate it to where I want it to be. Typically I'd have it so the last frame in the animation is the only one with the element at the angle that I rotated it to and then I would tween it with the previous frame to create motion. The problem I'm encountering is that I will have one frame (the last one on the timeline) selected, rotate the element that I want to rotate, and then the object rotates on all the frames previous to the one specific frame that I am attempting to alter. I can't create motion because when I alter the element in one frame it gets altered the same way in all of the previous frames, not just the one I have selected. I have no idea what to do and it's incredibly frustrating.