qpDeltaMap in NVENC 5.0.1 SDK samples

I’m trying to use qpDeltaMap in NVENC 5.0.1 SDK samples NvEncoder and NvEncoderLowLatency. According to the SDK qpDeltaMap “specifies the pointer to signed byte array containing QP delta value per MB in raster scan order in the current picture. This QP modifier is applied on top of the QP chosen by rate control.” But I see it hapenning only in the very first frame at some rate control conditions. The rest of the frames do not seem to follow the map at all. How in more details the map is applied to the QPs calculated by the encoder? What needs to be done to get it working? Is it a bug?