I recently spend two days try to figure out why Quick Parts in my Word document were failing to connect, update or communicate with the SharePoint Server. Were they had been working perfect for days they were now silently ignoring all changes I made to 'Shared Columns' inside my custom Document Set.
The reason was perplexedly simple: there was an (accidental) space in internal name of a column.
This innocuous little space caused the whole Document Set to become silently estranged from SharePoint to Quick Parts interactive. Even removing the offending 'share' did not resolve the issue.