As you say it worked for 3 days and then you get the error again – to me it seems like a connection issue between agent and application.
I know that UC4′s Agent for SAP can handle those dependencies between BI chains and can also do postprocessing and child-tracking for the chain (as sometimes the chain tells it was okay but when going through the output/log file there are error-messages that indicate that it was not okay – that’s what I’ve seen at several customers I worked for). Also you get sophisticated re-start mechanism where you can restart the chain at the point of failure (even automed re-start is possible) instead of running the whole chain again in case of failure.
Let me know if you’re interested in further information.
UC4′s website is www.uc4.com