Hi Markus,
I would check whether there's a Firewall or any traffic monitoring between the WFA server and the filers.
This is not releted to the WFA platform directly but a networking event.
Also bear in mind that if you suspect that the failure is momentarily - You can go to execution statues and try to resume the workflow:
It would retry the same failed command (From it's beginning, so if the command did something you may need to clean that).
Best,
Yaron Haimsohn
WFA Team