I'm seeing this issue on version 5.17.1 running on Windows 10.
I am *not* seeing this issue on version 5.11.1 running on Windows 7.
I've been digging through the source code for a bit, but am not familiar enough with the project to be able to determine what might have changed. This could be Windows 10 related...I'm just not sure. I am not at liberty to upgrade the WinSCP version on Windows 7 at this time to test whether the problem would appear.
My temporary fix was to try and find a registry setting that allowed me to increase the "FDDDeleteDelay" default setting of 120, but it appears that's not possible as far as I can tell.
Is there any other way to modify or workaround that timeout (or alternatively, determine whether this is a bug or expected behavior?)