I'll get back to you soon when I encounter the error again (I'll try until i get it). The server is a server which i have no access to (an FTP server from my University faculty).
A related thread was already created in the past, though as per to unspoken forum rules, I refrained from necro posting especially with the fact it was many years ago. Such is the link: https://winscp.net/forum/viewtopic.php?t=7488
What is particularly similar with me and the OP is that this happens randomly. Though however, to the best of my attempts, this may be a problem with the server and not with my personal setup as this can also happen on other different machines and clients too! Fortunately, "Retry" works and the files will resume download with their integrity intact.
Which is why I wish for auto-retry to work for this particular error. It would be nice to be able to download huge files without having to attend the program.
An alternative FTP client would able to auto retry on error. But hey I love this client more!
Sorry for the wall of text, as mentioned earlier, I will come back with a session log