I originally encountered this issue with downloading a 1.3GB tsv file and have been able to consistently repeat this error attempting to download a 2GB iso file from my SFTP server.Received too large (2999993 B) SFTP packet. Max supported packet size is 1024000 B.
Copying files from remote side failed.
Changing the Transfer preferences to a speed limit of 1024 KB/s doesn't cause any issues. Once the download speed goes above 1MB/s the connection is aborted.
I also tested using FileZilla and the web page interface of my SFTP server, I was able to reach 60MB/s+ through both methods.
Using Windows 10 Enterprise
Issue is consistently repeatable on WinSCP 5.21.5 when reaching any speed above 1024KB/s
Using SFTP, Server does not allow SCP.
Using Commander GUI