Pasting formatted text intermittently pastes without expected formatting
If text is inadvertently pasted within a style code, the text will lose all formatting and assume the formatting of the style.
Hit Undo (toolbar undo icon, Ctrl+Z on keyboard or Edit menu > Undo)
Click outside the style / further away from the styled text and re-paste
If unsure, enable Reveal Codes (View > Reveal Codes or Alt+F3) to see if the insertion point is within a style.
This has been seen in files with many styled areas in small spaces such as are created using the Monthly Calendar under File > New from Project.