Make sure the Custom Property Part Number Note $PRPSHEET:"PartNumber" is the same as the Custom Property in the part file. Everything needs to be exactly the same..
Check also the Configuration Specific properties. If there is the same Property Name in "Custom" and "Configuration Specific", the property in the config. spec. has the priority.
Along with John and Sergio's comments, also check the configuration properties (select the configurations tab in the tree and RC and select properties). Verify that the option under 'Bill of Materials Options' has not been set to 'User specified name'. I had a file that would not rename itself no matter what I did, after a lot of headache I found this to be the cause.
Thank you so much!
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