These duplicate entries are caused by duplicates in the Calendar table in Microsoft SQL.
Every time the program is opened it checks to ensure it has entries in the Calendar table and if not it populates the Calendar.
On rare occasions, the software fails to read the Calendar table successfully and populates the table with an extra duplicate set of dates. As the Manufacturing list views rely on information from within the Calendar table the entries within them get duplicated.
To resolve the problem:
DELETE FROM Calendar
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