Our A/P group reported an issue when a line on the Expense Report Export Program showed up indicating "Expense Report Line and Distribution Totals do not match" while the table AP_EXPENSE_REPORT_HEADERS_ALL showed "EXPENSE LINE DIST MISMATCH" for the REJECT_CODE. This was news to me as I had not seen it in R11 nor the past three months we had been running on R12 so off to My Oracle Support I went, and I found document 1582981.1 entitled "Expense Report Export Rejection: Expense Report Line and Distribution Totals do not match". This has the patch or patches which may have caused this, one of which WAS in our system, matches our exact error messages/text, and has additional SQL statements which allow you to verify if this note applies to the data in your tables.
You have two options to fix this, as you do with most issues found in MOS: patch or get a datafix. Luckily after submitting the information requested in this note via the SR process, the Oracle analyst indicated it was a rather simple datafix and after applied it DID resolve the issue at hand. I wanted to highlight this problem because the cause of it as detailed in the MOS note needs to be in your testing suite if you're on or thinking of going to R12 since it could be more frequent for your shop or happen a lot sooner after implementation.