This TEKLYNX CENTRAL article explains why default product variables in the browser interface revert back to label template default values after synchronization.
The default values entered in the TCAdmin interface for a product assigned to a particular label will revert back to the default values for that label after synchronization. This happens after the label template is updated with a change in the When Printed data sources.
This is by design. During the Synchronization in the TCAdmin interface, TEKLYNX CENTRAL scans the label templates assigned to products. If an approved label template has an updated When Printed data source, TEKLYNX CENTRAL will remove the previously entered default values and replace them with the label templates default values embedded in the When Printed data sources.
The software is performing as designed (but not as expected). There is a way to recover from this problem. Export the content of the table containing the related data, run synchronization and import the data from earlier export.
Note: the solution is purposely non-specific. The solution is not recommended. If you wish to deploy this solution, please contact us.
This was reported to Nick at TEKLYNX on July 16th, 2015. He said he would request development at TEKLYNX look at it for a possible future enhancement.