Inconsistent Steam error: Unable to extract flash vars

[kriskropd]

Make sure you are using the latest version: run youtube-dl --version and ensure your version is 2018.04.03. If it's not, read this FAQ entry and update. Issues with outdated version will be rejected.

• I've verified and I assure that I'm running youtube-dl 2018.04.03

Before submitting an issue make sure you have:

• At least skimmed through the README, most notably the FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones
• Checked that provided video/audio/playlist URLs (if any) are alive and playable in a browser

What is the purpose of your issue?

• Bug report (encountered problems with youtube-dl)

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If the purpose of this issue is a bug report, site support request or you are not completely sure provide the full verbose output as follows:

└───>youtube-dl --verbose "http://store.steampowered.com/app/635670/EMPORIUM/"
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'--verbose', u'http://store.steampowered.com/app/635670/EMPORIUM/']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2018.04.03
[debug] Python version 2.7.13 (CPython) - Linux-4.10.15-1-pve-x86_64-with-debian-9.3
[debug] exe versions: ffmpeg 3.2.10-1, ffprobe 3.2.10-1
[debug] Proxy map: {}
[Steam] 635670: Downloading webpage
ERROR: Unable to extract flash vars; please report this issue on https://yt-dl.org/bug . Make sure you are using the latest version; type  youtube-dl -U  to update. Be sure to call youtube-dl with the --verbose flag and include its complete output.
Traceback (most recent call last):
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 785, in extract_info
    ie_result = ie.extract(url)
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/common.py", line 440, in extract
    ie_result = self._real_extract(url)
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/steam.py", line 87, in _real_extract
    'flash vars'), playlist_id, js_to_json)
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/common.py", line 808, in _search_regex
    raise RegexNotFoundError('Unable to extract %s' % _name)
RegexNotFoundError: Unable to extract flash vars; please report this issue on https://yt-dl.org/bug . Make sure you are using the latest version; type  youtube-dl -U  to update. Be sure to call youtube-dl with the --verbose flag and include its complete output.

...
<end of log>

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Description of your issue, suggested solution and other information

This issue doesn't seem to be consistent across all of Steam as some other pages will collect the preview videos just fine. For instance, this one works: youtube-dl "http://store.steampowered.com/app/402750/Giant_Machines_2017/"