Bitrate is much higher than maximum configured with Video_Codec_SDK_12.2.72, comparing to 8.0.14

Hi,
We have been using Video_Codec_SDK_8.0.14, setting the maximum bitrate for the encoder, using

NV_ENC_INITIALIZE_PARAMS.encodeConfig.rcParams.averageBitRate

We want to upgrade to Video_Codec_SDK_12.2.72, but the bitrate we get is not limited, as if this parameter is ignored.

Specifically for I-frame we saw a major difference between old and new sdk - the I-frame itself is very large vs the other frames, we were trying to set qp limit and got with minimal effect.
We need the i-frames to be similar in size to the p-frames, and not have major fluctuations.

How can we limit the bitrate using Video_Codec_SDK_12.2.72?

Note: Using nvidia-driver-560 on both cases.

Thanks,
Adi