The term is not valid term SharePoint 2010 Managed Metadata

For example when you restore your SharePoint site to development environment from production, you should restore managed metadata service database as well. Then only metadata works fine and it will synchronize with SharePoint site database.

Update Managed Metadata service database (to fix invalid term set)

1. Take a backup of production managed metadata service database
2. Restore to your development server or where ever you are working
3. Go to central admin site, create a new managed metadata service or update existing metadata service database name field with your recently restored database name.
4. If you have created a new metadata service, you have to check the checkbox of that newly created service to the web application.

Central Administration>Application Management>Service Applications>Manage service applications

>select Managed Metadata Service> select Properties from ribbon

Update "database name" field as shown in  screenshot

Associate newly restored managed metadata service database here.

if you have created a new service then you have to associate a service to the web app.

Last step:

Run the metadata service related jobs for immediate effect or you can see next day morning with out any  invalid term set errors.

you have to go to each document library and configure terms one more time.

related post
http://suryapulipati.blogspot.com/2013/10/the-sharepoint-item-being-crawled.html