Hi Mark
Have you checked the Journals Term List for your library? This is the master list of titles used by the output styles and errors in it will be reflected in your bibliography.
To edit the Journal Term List go to Tools Menu, Open Term Lists, then Journal Term List. You will then see a listing of the journal names, select the title by clicking on it, followed by the Edit button. Make any changes here and then click OK to save the changes. Occasionally just editing the Full Title box won’t activate the OK button, click to one of the other fields and add an abbreviation too - this will always activate the OK button.
The other way to avoid problems like this to load one of the many predefined term lists which are available when you begin a new library.
Hope this will resolve your problem.
Kind regards
Patti