IPI must be initiated based on the discussion and alignment between the factory and the factory auditor once the production date is fixed, but you must focus that the shipment can not be done before the IPI was finished and OK.
That's the diffrence between IPI and the regular inspection, but there is another case that the regular factory inspection will be done if there is no production for UL approved products for a long time after your UL file was released.
Anyway, I assume there is misunderstanding between your factory and the UL factory auditor.
You gave the auditor cash, I disagree, but no need to appeal, and next time, pay attention to the communication with the auditor.
And I also assume your factory does not locate in Jiangsu province, cause normally, in Jiangsu, most of the auditors are nice, especially for the IPI.
Anyway, whereever the auditor is coming, I hate this kind of auditor, rubbish!!!
If I were the auditor, I will try to help the factories, and I will also accept the presents and cash, but that is based on the good relationship and communication with the factory, in other words, the factory apprieciates me and I respect the factory.