Hi Martin, so sorry this took such a long time to get back to you, i never got a notificaiton email from your server.
i made a log file with winscp 5.5.6 and attached it below.
there's something interesting when i look in it, i did a move command on a single file for testing and i think i found the reason why it always fails:
. 2015-01-27 14:29:26.842 Moving file "test.txt" to "/share/HDB_DATA/hdd2/test.txt".
> 2015-01-27 14:29:26.842 Type: SSH_FXP_RENAME, Size: 71, Number: 176914
isn't the rename command only for a local file or move something on the same drive as the source ? if that's the case then a simple comparison of the source and dest drive would solve this problem.
Or better yet, 1st try rename since its faster on single drive moves, and if it fails don't show a popup but try a move instead, then if that fails show a popup.
ps: i hope you can fix the email notifications, i've been registered here for a sufficiently long time and no notifs at all. you may want to check with your isp if they have changed ports or enabled some extra security that prevents out going emails.
pps: i see there's a newer winscp version 5.6.5rc i'll do the update toute suite and see if the bug still appears...