JavaScript works in HTML, but not ReviewLink

I have a JavaScript I use that "appends" images, buttons, and other elements to an image inside a scrolling text box. The JavaScript looks for an element with the class "textfield", then sets the positioning relative to the "0,0" of the image in the text field.


In testing, this has worked flawlessly in all courses up until this one I'm working on right now. I have not changed any of the code I'm using (I'm using Library Objects to make the process of attaching the RunJS easier). I'm completely stymied as to why this is happening, especially when things function correctly in HTML, but fail miserably in ReviewLink.


Any insight is appreciated, and sample files and invites to the course up on ReviewLink are readily available.