looks like this problem is still not solved in the last version 3.0 build 159. as it was reported before
https://winscp.net/forum/viewtopic.php?p=910
now program does not crash but insted acts quite strange.
to produce this error you need a linux box with groups. make one file owner a person A and group A and file permissions
rw-rw-r--
now as a user B that exists in group A you should be able to overwrite this file since it has u,g - rw permissions even if the owner is user A from the same A group with you (user B), right?
when you try to overwrite the file the error message appears
scp: /usr/local/apache/htdocs/public_html/images/style.css: set mode: Operation not permitted
you can click whatever button you like but you will get only one message
Unexpected directory listing line
after that the program does not crash but shows clear window with no directory listing at all.
if you click refresh it shows another message
Command "pwd ; echo "WinSCP: this is end-of-file:$?"" failed with invalid output "".
and nothing happends again...