@Guest: That likely falls under:
Issue 227 – Asynchronous program interface
Unless you believe the UI hangs longer than the loading is happening.

There's something similar during directory loading with FTPS (I didn't test others) but the WinSCP window is frozen in place and can't be moved until after directory loading is finished.

In effect, its frozen, or a hang without the actual hang happening. It has the same feeling as a hang in the end. This is a UI issue and the window should still move during directory loading.

Windows 11.

I have added this issue to the tracker:
Issue 2309 – Stall when switching from S3 to other protocol on Login dialog on some networks

Thanks for your report.
I have sent you an email with a debug version of WinSCP to the address you have used to register on this forum.

When I start WinSCP and click a site from the Login screen, the mouse icon changes to the 'processing' icon and WinSCP hangs for roughly 20 seconds. A single click on any of the sites on the list is enough for this to happen (the login doesn't even start yet). If I try to close the window I get a 'this program is not responding' prompt. After about 20 seconds it all gets 'released' and I can continue logging in.

This doesn't happen every single time but it happens very, very often. I cannot see a pattern as to why and when this is happening. I did notice that when I log into Amazon S3, it never happens. But any other site I log into (SFTP file protocol), it happens very often.

This issue started a few months ago after upgrading WinSCP to the latest version at the time, and it won't relent ever since. I currently have the latest version (6.3.4) running on Windows 10, I've already tried re-installing WinSCP even with a fresh configuration (totally from scratch) yet this keep repeating regardless.

WinSCP version: 6.3.4
Windows: 10
Transfer protocol: SFTP
GUI: Explorer

Any idea how to fix this?
Thank you :)