We occasionally have MRP jobs in error with the following message 

Error snapshot MRP Supply/Demand. Site/Part/ABC Class ABC/123123123123/C. Source/Order MRP/29578848, *, *, 37. Original error ORA-20112: MrpPartSupplyDemand.EXIST2: The Mrp Part Supply Demand object already exists.

We do tick the ‘Stop on Error’ checkbox when running because if there is an error we want to know about it.  We’ve never completely bottomed out what set of circumstances have fallen into place that generate this error and generally put it down to maybe someone updating demand or supply manually or running MRP at the same time.  

Does anyone in the community know what particular processes/conflicts are taking place to generate this error?

Thanks.