It might be due to this workaround for FTP servers that send directory listing inefficiently:
Before posting, please read how to report bug or request support effectively.
Bug reports without an attached log file are usually useless.
No. FTP listing for a directory is downloaded as one large plain text stream. If your solution is to generate a text file with the directory listing and download that, you are basically doing the very same operation that FTP does internally. If your solution works quickly, but the listing download with FTP is slow, there's something wrong with the FTP server.
No - its not a server problem - its an ftp problem.
With ftp you step file by file through the directory.
Btw - to change the update rate in settings to 600 seconds does not work for me.
It is still working after several seconds and blocked for 5 minutes until it is back for some seconds when the showed folder has 9800 files