It may be obvious to techies like me I suppose, but there is a font for the 'music bits'. It may however not be an installed font in Windows, but just local to the particular program, so that what gets exported is just a series of number indexes to a font that windows substitutes one of its installed fonts for. That's the Generic Answer!

If you check up on the documentation for your program - I don't use it so I am not familiar with it - you should see if there is supposed to be a font that apparently is not installed currently in Windows. You can then check the Fonts installed - the particular font file might be damaged - and reinstall it if necessary.