My solution was to temporarily move the .filezilla file, you will find it in your users directory: users/your-user-name/.filezilla
It is a hidden file, and to view hidden files:
defaults write com.apple.finder AppleShowAllFiles YES; killall Finder /System/Library/CoreServices/Finder.app
Once you can see the file, move it
Restart Filezilla and the window will have been restored to the center of the screen.
You will find that your settings no longer exist, at this point copy back the xml file: sitemanager.xml to the newly created .filezolla folder.
NOTE: You may find that filezilla has a new location for its files: users/your-user-name/.config/filezilla