FTP & RDP issues with D50D

We are running a fleet of Dell D50D thin clients which are configured via DHCP option flags to access an FTP server for firmware updates and .ini files.  I am in the process of replacing server on which the FTP server and files reside and have noticed an interesting situation in the FTP logs.

It seems that the thin clients consistently fail to authenticate with the FTP server when they boot but are able to authenticate with the FTP server successfully when they are shut down (or rebooted).  The error is with the password – the failure is “530 login or password incorrect.”

It seems very odd that this is the case if the credentials are supplied by DHCP options – they should work both on boot and shutdown.  However, as I test, I set up a FileZilla FTP server to connect to as this allows me to view the passwords in the log files if I so choose and I noted that the password is indeed incorrect – it seems to be adding a backslash before special characters.  For instance, “pas$word” becomes “pas\$word” – and this fails to authenticate (again, only on boot).

I updated to build 11.3.110 on one thin client and the FTP login problem persists.  Oddly, if the thin client detects a new raw image file at shutdown, it will correctly log into the FTP server on restart and download the update!

We have also discovered that RDP is broken on 11.3.110; we cannot RDP into Windows Server 2016 – we  only get an error message “resource initialization error”.  Windows Sever 2012r2 and Windows Server 2019 are unaffected.  Since our terminal servers are all Windows 2016 we will not be able to roll out 11.3.110 until this is resolved.

Any help is much appreciated!