Dear OP,
Alt.Binz will create the file even if incomplete once all retries have been attempted, and then repair with par2 if available. This is standard behaviour.
As ever, if you have a specific example that's causing problems, first read your Log, then list the steps here to reproduce it so that it can be debugged. Generic "it doesn't work sometimes" posts are really no help at all.
Regards,
Hecks