This can often happen when you are copying and pasting content from one location to another. In most instances utilizing the clear formatting option in the menu bar (large italic T followed by a small subscript X) will resolve this issue. Sometimes you may need to reapply a style after clearing the formatting. You can do this by using the drop down menu bar item where formatting styles are listed (paragraph, heading 1, etc.).

>>Learn more about options available in the Rich Text Editor in Canvas.