AP Terms Changing At Voucher Entry

Good morning everyone.  I have an interesting problem.

We are on E1 9.0 running tools 8.98.3.  During voucher entry, periodically, the terms that were pulled in from the vendor master are changing.  As an example, vendor ABC has terms of net 30.  After entering a purchase order, I confirmed in both the header (F4301) and the detail (F4311) that the terms are net 30.  After receipt, I confirmed in the PO Receiver table (F43121) that the terms are net 30.  After vouchering, sometimes, the terms have changed to say net 45 in the AP Ledger table (F0411).  It does seem to happen more often with some vendors, but