Unified folder view slow to update, and "not responding"

I have several errors associated with the unified folders display. I have 6 email addresses coming in to Thunderbird. 3 are IMAP and 3 are POP. I have the POP addresses consolidated into the "Local" Folders Inbox, Sent, Trash etc. In the "All Folder" account views, the Local folder correctly displays one Inbox, one Sent, one Trash etc. The 3 POP emails accounts are being consolidated appropriately. However,in Unified folders, the Local folder as well as all of the individual POP addresses are now listed for the Inbox, Trash and Junk folders. There is now no consolidation. Also, the Unified folders themselves are extremely slow in working. Accessing the properties for the Unified Inbox, Trash or Junk folders results in a long wait with Thunderbird entering a not responding state. Right click operations on the unified folders do not work at all. I cannot select properties, I cannot mark as read, empty or otherwise manipulate the folder. I must go to the individual accounts to manage any folder content. Which I would think makes the whole concept of Unified folders moot. I am not at all certain what may be the root cause of this rather longstanding problem. I have deleted the smartfolders directory, have deleted the virtualfolders.dat and foldercache.json and foldertree.json files. Nothing seems to work. Any suggestions?