Change Connected Servers
Make sure the password is cleared in your login Keychain. Open the Keychain Access utility (spotlight > Keychain Access). IN the left hand panes, select Keychains > login and Category > All items. Now search for diskstation in the top right to filter the results.

Delete the offending keychain entries.

Change the username and password for these entries so as not to disrupt anything else going on with those servers.