WinSCP 5.13.5 (build 8967) Can't create a directory.

OS: Win 10
WinSCP: 5.13.5 (Build 8967)
Protocol: SFTP
Port: 2222 (iPage website SFTP connection port)
Issue:
While I can successfully login to my iPage domain and transfer files into already existing directories, I can not create new directories (I can delete existing directories) either using the F7 key, or by selecting from the menu.

I've shut off my VPN and firewall and still see the same results. If I create the directory using the iPage web interface, I can download files into the newly created directories, but again can't create any subdirectories.

I tried opening a putty terminal to run the "mdkir -m7555 Junk" command and received the message that no pty access was granted by the remote system.

I've been in contact with the iPage technical support and they claim they were able to create a directory using Filezilla (I confirmed the directory was present) using the SFTP protocol. I don't know what's different about the SFTP implementation that might cause this issue.

I have attached the log file to this issue.

. 2018-12-10 17:57:43.922 Canonifying: "Junk"
. 2018-12-10 17:57:43.922 Getting real path for '/Junk'
> 2018-12-10 17:57:43.922 Type: SSH_FXP_REALPATH, Size: 15, Number: 7184
< 2018-12-10 17:57:43.938 Type: SSH_FXP_STATUS, Size: 33, Number: 6412
. 2018-12-10 17:57:43.938 Discarding reserved response
< 2018-12-10 17:57:43.938 Type: SSH_FXP_STATUS, Size: 24, Number: 6660
. 2018-12-10 17:57:43.938 Discarding reserved response
< 2018-12-10 17:57:43.998 Type: Unknown message (0), Size: 62, Number: 1327
. 2018-12-10 17:57:43.998 Attempt to close connection due to fatal exception:
* 2018-12-10 17:57:43.998 SFTP protocol violation: Invalid response message type (0).

The SFTP server violates SFTP specification by sending an invalid response to SSH_FXP_REALPATH request.
In turn, FileZilla is known to violate SFTP specification by not using SSH_FXP_REALPATH request, so it does not hit the server's bug.

Thank you Martin. I'm not an expert in the SFTP protocol so your explanation is very helpful. I will speak with iPage and hopefully get this resolved.

Sincerely,

Brian S. Wilson