Start with Debug 1 level log and we will see if that's enough. Thanks.

Does it matter what level of logging I do?

To generate the session log file, enable logging, log in to your server and do the operation and only the operation that causes the error. Submit the log with your post as an attachment. Note that passwords and passphrases not stored in the log. You may want to remove other data you consider sensitive though, such as host names, IP addresses, account names or file names (unless they are relevant to the problem). If you do not want to post the log publicly, you can mark the attachment as private.

How do I post a session log file?

The OP of the other question was not getting any error message. The problem there is about rendering of the files in the GUI. While if you are getting a message that suggests turning off the buffer optimization, you likely have problems when retrieving the listing from the server. So very different problem. Please start by posting a session log file.

Forgot to say I also tried this. The error message said to try this.

The Optimize connection buffer size enables optimization of socket buffer size. It greatly improves transfer speed. Disable it only when experiencing problems. The option is not available with WebDAV protocol.

https://winscp.net/eng/docs/ui_login_connection

WinSCP is freezing/crashing when directory contains 5000 small files. I saw this post:
Slow/crash with directory containing ~130,000 small files

Can I please use the debug version? I will also try FileZilla and double commander. Do I need to provide any debugging info?