3814600 - Error: One or more blocking exceptions are preventing approval submission. Resolve the exception before proceeding.

We faced one issue that for some expense report, when processor click "Approve" button, one red exception appears as "One or more blocking exceptions are preventing approval submission. Resolve the exception before proceeding." However, on this report header ONLY display warning messages triggered by audit rule instead of red message from stop audit rule. We cannot find red icon on each expense entry either. May I know why this happened?

Cannot Process Expense Report , KBA , CON-CA-ADM , Administration , Problem