Within the last month, I have had no less than 6 data files submitted to me for analysis and/or repair which evidenced Overflow Errors in transactions after upgrading to a 2015 version of QuickBooks (including QuickBooks Enterprise 15).
Overflow errors typically occur in the Items list, and on rare occasion in a specific 'account' of the chart of accounts, but you normally don't find them in individual transactions. In all of the submitted files individual transactions had overflow amounts in one or more items within the transactions and/or within the transaction as a whole.
If you are seeing any files of this nature, please let me know by posting a comment to this article.