Do you have the responsive text option set and if so is the LMS displaying the LO in a smaller window that you view when viewing direct from Xerte? Do you have an option to set the SCORM to open in a new window and if so does that make a difference?
HTH
Ron
Could be. Inspect the text that is changing using the browser developer tools and see if there is a style sheet loading and affecting the Xerte styles.
HTH
Ron