youtube_dl (v2021.06.06) get duration fails if server runs in nginx (502 bad gateway error)

I have a web server which uses youtube_dl.extract_info to get video length. It works well for long time, but begin to fail in last 3 months. After upgrading to (v2021.06.06), it still fails. See sample code below.

      import youtube_dl

      def get_duration(self, yt_video_id):
        ydl_opts = {
          'format': 'bestaudio/best',
          'outtmpl': 'tmp/%(id)s.%(ext)s',
          'noplaylist': True,
          'quiet': True,
          'prefer_ffmpeg': True,
          'audioformat': 'wav',
          'forceduration':True
        }

        with youtube_dl.YoutubeDL(ydl_opts) as ydl:
          try:
            ret_dict = ydl.extract_info(
                "https://www.youtube.com/watch?v={sID}".format(sID=yt_video_id),
                download=True)

          except Exception as ex:
            err = 'Exception: get_duration. ' + str(ex)
            print(err)

        return ret_dict['duration']

When it fails, "except Exception as ex" block does not catch the exception.

The get video length code is in a rest API with Ajax in UI. Ajax error block catches the error with followings:

<head><title>502 Bad Gateway</title></head>
...
<h2><center>nginx/1.14.0 (Ubuntu)</center></h2>

===Javascript code
let defer = this.myRestApiCall('POST',...);

defer
.done(function(data) {
   // code here to handle success.
}.bind(this))
.fail(function(data) {
  alert('Save failed!' + data.responseText)
}.bind(this))

If running same code NOT behind nginx, it works.

Questions:

1. How to solve it?
2. Why Python catch block does not catch the error?