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've had this error before when using multiple servers/providers. Seems to happen when sabnzbd downloads different files from different servers and trying to assemble them. All server copies technically should be identical but it doesnt seem to be the case. It stopped when i cut out all the other newsgroup servers. By servers I mean different providers.