webrtcbin: h264 decoding problems with chrome/firefox

Hi, I got a strange h264 decoding issue. It seems it is not a proper issue board to discuss. But, the webrtcbin is a complex architect, I have to ask help here. Any suggestion will be appreciated. Thanks in advance!

My problem is: We write a python client(based on gst-python) to subscribe/publish from janus-gateway. When we do publish from an firefox/chrome browser, and then do subscribe from janus-gateway. It will show many h.264 message like this:

0:00:30.279190215 24831      0x14c6ca0 ERROR                  libav :0:: non-existing PPS 2 referenced
0:00:30.279198476 24831      0x14c6ca0 ERROR                  libav :0:: decode_slice_header error
0:00:30.279202932 24831      0x14c6ca0 ERROR                  libav :0:: no frame!
0:00:30.279210819 24831      0x14c6ca0 WARN                   libav gstavviddec.c:1975:gst_ffmpegviddec_handle_frame:<avdec_h264-0> Failed to send data for decoding

More information are:

Switch to vp8 codec works fine.
Publishing from another python-client(which act as publisher) works fine. (we use testvideosrc)
The full pipline diagram looks like

So, any comments for this? And my further questions are:

Can I switch to openh264 from decodebin2?
Is there any potential issue from h264parse?