Hi,
Not sure if it help but please apply this prebuilt lib for a try:
Jetson/L4T/r32.5.x patches - eLinux.org
[camera] 3rdparty application fails to open with USB camera
And may also try to launch a pipeline through gst_parse_launch(). Here is a sample:
GStreamer freeze when using qtmux and NVIDIA-accelerated h264/h265 encoding - #7 by DaneLLL