[schapplm]

What you can try is:

• copy the database file to a local folder and set WatchedList to use that local database file. By this we can check if this is related to the file itself or the network access (which could e.g. corrupt the file while copying with wrong permissions)
  
• If the problem seems to be the file: Open the database file with a program like sqliteman, as described in the wiki.
  
• If you can open the file with the other tool but not with Kodi/WatchedList, then it might be a version issue of the python sqlite3 module. Then the easiest thing for you is to create a new file: Just set the addon to use a file that does not exist and start it. After the first run which creates a new file, you can insert your data from the old file again using Export/Import syntax similar to this wiki subsection