I've just noticed that all the folder sizes while using ftp are all 4KB not the calculated sizes.
Has a setting changed in v11.3 
Opus just reports the sizes that the FTP site itself reports. They are the sizes of the directory listings (more or less), not the sizes of the data in the directories.
You can use Edit - Calculate Folder Sizes (Ctrl-L) to calculate the size of the data, as with a normal folder.
(None of this is new in 11.3; it's been this way for years.)
it seems its not all ftp sites that do not list directory sizes.
It's up to the FTP server what it sends back in the directory listings. Opus just reports what it gets from the server, until you override that by asking it to calculate the sizes itself.
It seems when I log in to our server if I use usernames it gives the directory sizes but if I log in using the root username it doesn't in the home directory, not even directories that do when using their usernames to get there..