Cannot search in some folders in Email Center

Goldmine PE 2015

One user reorganized some of his emails in the Filed and Sent folders. He created some new folders and moved some of the emails from the auto filed folders.

e.g. Moved emails from the "November 2016" folder into a new folder called "Follow Up"

After the move, he can not perform a search for emails that are now inside the "Follow Up" folder. When a search is performed, it just keeps searching without any results.

Has anyone come across such issues and have any suggestion on a fix?

Thanks