Part numbers.... the 14mm sealing washer for the oil lines to the tank is 94109-14000 The sealing washer for the drain plug on the oil tank and on the pan is 12mm part number 94109-12000 maybe a PO put the wrong one in? The O-rings for the engine end of the lines is 15 x 2.5mm and is part number 93102-377-000
The lines are discontinued says servicehonda, best of luck finding the simplest cause for your leakage.
A quick check of Davidsilver, Cmsnl and Yamiya confirm Zero availability on non NOS, OEM style oil lines.