The same frame appears in cuvid decoding

Under the windows platform, I use the videocapture of ovpencv to collect data, set it to YUV420 format, encode it with the cuvid SDK, set “- GOP 5” on the command line of the encoder, and then use librtmp to push the stream to the SRS server.
I use librtmp to pull the stream, save it as a flv file, decode and play it with cuvid SDK. It is found that the first frame will appear every five frames. When playing with ffplay and VLC, the first frame will not appear repeatedly.
I did the test with the SDK’s built-in example code, and did not modify any other parameters.
i am using Video_Codec_SDK_11.1.5, rtx1650, win10,

I found the location of the bug, but I couldn’t solve it. According to the SDK’s built-in example, av_bsf_send_ packet,av_ bsf_ receive_ packet for data filtering. I write the data filtered by these two functions directly into the MP4 file and play it with ffplay. The first frame of repetition appears.