How to resolve Universe generation failed for BOBJ reports?

Hi,

Wea re having BOBJ reports which is using BEx queries as an backened. Recently there was upgrade in BW system from SP3 to SP18. Before upgrade all the reports works fine. But after upgrade we are getting error while refreshing the reports and this issue is on every alternate run. Please help to understand what might be the issue.

BOBJ version - 4.2 SP5

Thanks