BQ25703A: The current limit set is not pricise

Part Number:BQ25703A

When the chip work under OTG mode, the otg current is set to 3.6A. I set the electronic load to 3A. It works well under OTG voltage is 5V and 9V and it fails under 12V. It works at the beginning but fail after a little later. The voltage keep dropping and drop to 0 at last. When  I enlarge the otg current to 4.2A. It works well under 12V. Why the current limit error is so big? What can I adjust?

Thanks

BR

Ren