I can not access (from Thunderbird) and see contents of some (a few) of my Thunderbird Mail Archive archive subfolders,
I can not access (from Thunderbird) and see contents of some (a few) of my Thunderbird Mail Archive archive subfolders, while the contents of many other subfolders are perfectly visible. I can easily access them in File Explorer, though. When I am trying to access them from Thunderbird it takes a lot of time (many minutes) of mouse pointer dice rolling and then it opens an empty folder filled with some ghost empty lines instead of stored emails. Just to mention, before accessing those subfolders Thunderbird shows some pretty realistic (usually large enough) number of unread emails there. It looks like those subfolders are somehow corrupted. Can they be restored and made accessible? Thank you.
What is your anti-virus software?
It sounds like your mail files are corrupted. First of all create a backup of your Thunderbird profile folder. https://support.mozilla.org/kb/profiles-tb#w_backing-up-a-profile
Then try to rebuild the index file of the troubled folder. Right-click the folder - Properties - Repair Folder
Note: depending on the state of corruption this may erase messages from the affected folder which cannot be recovered anymore. In that case you'd need to restore them from a recent backup done prior to the corruption.
Corruption is often caused by anti-virus software messing with Thunderbird mail files. It is therefore recommended to create an exception for the Thunderbird profile folder, so that the real-time scanner won't attempt to scan the profile with your mail.
For more information on the profile location see http://kb.mozillazine.org/Profile_folder_-_Thunderbird