Why does it happen?
Because the new default for encryption in Filezilla is set to 'Use explicit FTP over TLS if available'.
The Solution
- Open Filezilla
- Click on the 'Site Manager' icon or click the 'File' menu and then 'Site Manager' or press Control+S.
- On the 'General' tab there's a selection list right to the 'Encryption' setting, click on it.
- The default setting, which is causing the slow uploads and downloads is the first one at the top, 'Use explicit FTP over TLS if available'.
- If you want to speed things up select 'Only use plain FTP (insecure)'.
- And, as it is stated in brackets, this type of encryption is insecure, and snoopers could intercept the data transfered.