Try editing your server appdata/crashplan/conf/my.service.xml file, around line 23 may say:
<serviceUIConfig>
<serviceHost>127.0.0.1</serviceHost>
If necessary, change this to:
<serviceUIConfig>
<serviceHost>0.0.0.0</serviceHost>
This makes crashplan listen to non host clients without the use of the ssh tunnel. Restart the Crashplan docker and the Crashplan-Desktop docker should now connect without issue. As this is less secure, once logged into crashplan, change the security settings to require a password to use the client.