If that can help, the "Device.Backup.Running Config" work fine and show exactly the same patern :
<NEWSESSION CatTools 3.11.2 11/08/2017 08:19:07>
<ACTIVITY TYPE=Device.Backup.Running Config>
<ACTIVITY SCRIPT=C:\Program Files\CatTools3\Scripts\Client.Device.Backup.Running Config.txt>
<USERS NAME FOR DEVICE=SSG5-Nogaro>
<C OK 08:19:08>
<R-08:19:08>Remote Management ConsoleSSG5-No32->
WFDRetVal=0. Waiting for: "acceptthisagreementy/[n]"
Opened a support ticket and got someone to help me.
It was the "Juniper.Netscreen.Firewall.txt" in the script folder who did not work with those juniper device since the last version.
He gave me an old version of this file and it corrected the problem.
In hope the problem will be solved in the next updade of Kiwi !