Cannot apply re-named Term to document library items - it reverts back to using the old Term

Question

Desired Behaviour

After renaming a Term in the Term Store Management Tool, I expect that items in a Document Library that have the OLD term as a Managed Metadata column value will KEEP that column value, for example:

Column Name:  Content Type  ​
Column Value:  Networking  <--------- this is the OLD term 

However, I also expect that when I try and Edit that item's column values, I should be able to choose the NEW term in order to update the column value.

Column Name:  Content Type  
Column Value:  Networking Event <--------- this is the NEW term 

Actual Behaviour

What is happening is that I can select the new term and, as the item saves, it reverts back to the OLD term value.

Steps To Reproduce

• Create a term called Networking
• Change it to Networking Event
• Change it back to Networking
• Change it to Networking Event
• Go to Document Library item and try and change it's column value from Networking to Networking Event
• It will look like it is going to save as the new term Networking Event, but then revert back to the old term Networking.

Environment

• Browser: Chrome Version 90.0.4430.212 (Official Build) (64-bit)
• SharePoint Online
• Microsoft Team SharePoint Site Document Library

Notes

• I have closed and reopened browser tab in case it was a browser cache issue
• I have checked and there are no 'Other labels' for the term, ie no other synonyms and abbreviations

Answer 1

As per my experience, you may find that the synchronization between the Term Store and the managed metadata fields in a list or library is not always as fast as you wish or even seems to not work at all. The reason for this is that there is a timer job called Taxonomy Update Scheduler, which handles the synchronization.

So, if we update the Term Store, we must take into account that it can take up to 24 hours for the Taxonomy Update Scheduler timer job to be triggered and synchronize the managed metadata fields. If after 24 hours checking the managed metadata fields haven’t sync, we should be concerned. Currently, in SharePoint Online, there is no way to force the timer job execution or any kind of workaround, since we don’t have control of this timer job which is managed by Microsoft.

A thread similar to yours: https://docs.microsoft.com/en-us/answers/questions/355756/managed-metadata-not-all-term-sets-displaying-corr.html