In October 2019 I implemented a flow to create a document set and update the managed metadata fields on the document set using the methods in this post: https://sharepointycl.wordpress.com/2018/05/07/updating-sharepoint-online-document-set-in-microsoft-flow-including-taxonomy-field/
It has worked perfectly since launch last year, but it stopped working July 2020. I have not changed the flow and I have not changed my SharePoint document set design.
Does anyone know what may have changed? No errors are thrown, it is just that the managed metadata column are no longer being updated. They stay at their default value.
Thanks for pointing me in the right direction.