OPA192: Current sample occurs the non-linear phenomenon

Part Number:OPA192

Hi Guys

Our customer is using our opa192 for 12Vout high side current sample. Please see below the schematic:

But when test the load transient sample, we found that 12_Iout  non-linear phenomenon. Please see below the waveform:

CH1: 12Vout;   CH2: Io;   CH4:  OP_OUTPUT;

So why are there non-linear section at the transient up-going?

Thanks

-Pengfei