Could you be more specific as the the errors you are receiving in the integrity check, regarding discounts? It may be that the record is corrupted and the 'first' field that appears out of whack by the check is the discount field. Or somehow a number got saved within the discount field of the batch when one was not expected.
If you first make a backup of your Payables data, you can attempt to Rebuild errors found by the Integrity checker. Some can be successfully rebuilt and others cannot. If it is as simple as an incorrect number was found in the discount field, these can usually be Rebuilt.
If rebuilding does not solve the problem, the choices are to restore the AP data from a good backup, or have the data repaired. You may also be able to delete the entry or the batch and simply re-enter it.
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Regards,
Softrak Tech Support