Do you experience problems during downloading?
Check your connection in Status and Interface settings window.
Use Test Server in Config > Servers.
We will probably ask you to do a test using only basic settings.
Do you experience problems during repair or unpacking?
Enable +Debug logging in the Status and Interface settings window and share the relevant parts of the log here using [ code ] sections.
I think this is a problem with name resolving. And that can be caused by a non-functional or unreachable nameserver, or by a network problem.
So check that.
And/or: create another server entry in SABnzbd, with '91.208.207.165' (=ssl-eu.astraweb.com) as news server, with your ssl-eu.astraweb.com credentials, and just one thread. If that keeps working all the time, it is a nameserver problem. If that has problems too, it is a network problem.