BI Publisher Scheduler failing for certain reports in 10.1.3.4 - java.lang.NullPointerException

When we set up a schedule it works for some time and then fails. We then need to create a new schedule and it then works for a number of days. We have other reports which run ok at a similar time.BIP Scheduler failing for certain reports. The report run fine standalone, but when scheduled it fails
BIP report, runs using a JDBC connection to one of our Oracle Financials Dbs.
Issue still persist after bouncing the OBIEE and Tomcat services.

Error log:
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oracle.apps.xdo.servlet.scheduler.ProcessingException: java.lang.NullPointerException
 at oracle.apps.xdo.servlet.scheduler.XDOJob.runBurstingReport(XDOJob.java:2116)