12c Unstable execution Plan causes long running Crystal Report

Hi All,

Using Oracle Database 12.1.0.2 on Solaris 10

We have a business report that is dynamically generated through Crystal Reports from the Vendor Application every day.

The Execution plan for this report is "randomly" flip-flops causing the report to run poorly when the bad execution plan is chosen by the optimizer.

I say randomly, but this could be for some unknown reason at this time. 

This report is run during a batch process and on weekends runs 2 times on Sunday. (Once for Saturday's data, then later in the batch for Sunday's Data)

Last few weeks the both Sunday runs have been stable using a consistent Execution Plan, but again yesterday, both runs have used a poor execution plan and ran slow.