After DL from YT, merge fails after warning message

[Baylink-gh]

Checklist

• [ x] I'm reporting a broken site support issue
• [x ] I've verified that I'm running youtube-dl version 2020.03.24
• [ x] I've checked that all provided URLs are alive and playable in a browser
• [x ] I've checked that all URLs and arguments with special characters are properly quoted or escaped
• [ x] I've searched the bugtracker for similar bug reports including closed ones
• [x ] I've read bugs section in FAQ

Verbose log

C:\Users\jra\Dropbox\Theatre>vdl -U
youtube-dl is up-to-date (2020.03.24)

C:\Users\jra\Dropbox\Theatre>vdl --verbose https://www.youtube.com/watch?v=-ZgBexrZvM0
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['--verbose', 'https://www.youtube.com/watch?v=-ZgBexrZvM0']
[debug] Encodings: locale cp1252, fs mbcs, out cp437, pref cp1252
[debug] youtube-dl version 2020.03.24
[debug] Python version 3.4.4 (CPython) - Windows-10-10.0.18362
[debug] exe versions: ffmpeg 4.2
[debug] Proxy map: {}
[youtube] -ZgBexrZvM0: Downloading webpage
[youtube] -ZgBexrZvM0: Downloading MPD manifest
WARNING: [youtube] -ZgBexrZvM0: Skipping DASH manifest: ExtractorError('Failed to download MPD manifest: HTTP Error 404: Not Found (caused by HTTPError()); 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.',)
[debug] Default format spec: bestvideo+bestaudio/best
[debug] Invoking downloader on 'https://r1---sn-5uaeznk7.googlevideo.com/videoplayback?expire=1588157308&ei=HAepXtnvBbb3zLUProCFwAU&ip=35.143.203.79&id=b84e11a9d6ef761c&itag=227&aitags=142%2C143%2C144%2C145%2C146%2C161%2C222%2C223%2C224%2C225%2C226%2C227%2C273%2C274%2C275%2C279%2C280%2C317%2C318%2C357%2C358%2C359%2C360&source=yt_media&requiressl=yes&mh=Fq&mm=31%2C26&mn=sn-5uaeznk7%2Csn-q4flrnee&ms=au%2Conr&mv=m&mvi=0&pl=13&gcr=us&initcwndbps=1887500&vprv=1&mime=video%2Fmp4&aid=f998017b1ad9bccd&asource=youtube&gir=yes&clen=5216436144&dur=6112.904&lmt=1541017860399303&mt=1588135596&fvip=1&keepalive=yes&c=WEB&sparams=expire%2Cei%2Cip%2Cid%2Caitags%2Csource%2Crequiressl%2Cgcr%2Cvprv%2Cmime%2Caid%2Casource%2Cgir%2Cclen%2Cdur%2Clmt&sig=AJpPlLswRAIgdF7FKRKa6vG_venHZ6kaiz1sLIJGc7-wLMmwsKxtYY8CIDia7grXgOOiBoaOVh6M0oeKtquZY6C11zd5meIli4t4&lsparams=mh%2Cmm%2Cmn%2Cms%2Cmv%2Cmvi%2Cpl%2Cinitcwndbps&lsig=ALrAebAwRQIgBbf4tesiPBsArwCD0Nlrci-1vHUiObMFmMBuNEHf6oMCIQCJF_8epA1WzxKgri48m0uLXgV2wYzc8YDA0kFlItloCw%3D%3D&ratebypass=yes'
[download] The Wrecking Crew--ZgBexrZvM0.f227.mp4 has already been downloaded
[download] 100% of 4.86GiB
[debug] Invoking downloader on 'https://r1---sn-5uaeznk7.googlevideo.com/videoplayback?expire=1588157308&ei=HAepXtnvBbb3zLUProCFwAU&ip=35.143.203.79&id=b84e11a9d6ef761c&itag=329&source=yt_media&requiressl=yes&mh=Fq&mm=31%2C26&mn=sn-5uaeznk7%2Csn-q4flrnee&ms=au%2Conr&mv=m&mvi=0&pl=13&gcr=us&initcwndbps=1887500&vprv=1&mime=audio%2Fmp4&aid=f998017b1ad9bccd&asource=youtube&gir=yes&clen=295046944&dur=6112.992&lmt=1541017548405475&mt=1588135596&fvip=1&keepalive=yes&c=WEB&sparams=expire%2Cei%2Cip%2Cid%2Citag%2Csource%2Crequiressl%2Cgcr%2Cvprv%2Cmime%2Caid%2Casource%2Cgir%2Cclen%2Cdur%2Clmt&sig=AJpPlLswRAIgDTLvkOzcB5jA6n2HSyLrsnasZdA-sY8np_1YkEJZWi4CIBnF0t-xrRz6tX9zU6r0qi1ZAjnRSYSFezhvUiWiDqqF&lsparams=mh%2Cmm%2Cmn%2Cms%2Cmv%2Cmvi%2Cpl%2Cinitcwndbps&lsig=ALrAebAwRQIgBbf4tesiPBsArwCD0Nlrci-1vHUiObMFmMBuNEHf6oMCIQCJF_8epA1WzxKgri48m0uLXgV2wYzc8YDA0kFlItloCw%3D%3D&ratebypass=yes'
[download] The Wrecking Crew--ZgBexrZvM0.f329.m4a has already been downloaded
[download] 100% of 281.38MiB
[ffmpeg] Merging formats into "The Wrecking Crew--ZgBexrZvM0.mp4"
[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:The Wrecking Crew--ZgBexrZvM0.f227.mp4" -i "file:The Wrecking Crew--ZgBexrZvM0.f329.m4a" -c copy -map "0:v:0" -map "1:a:0" "file:The Wrecking Crew--ZgBexrZvM0.temp.mp4"
ERROR: Conversion failed!
Traceback (most recent call last):
  File "C:\Users\dst\AppData\Roaming\Build archive\youtube-dl\ytdl-org\tmpjwbwqymm\build\youtube_dl\YoutubeDL.py", line 2065, in post_process
  File "C:\Users\dst\AppData\Roaming\Build archive\youtube-dl\ytdl-org\tmpjwbwqymm\build\youtube_dl\postprocessor\ffmpeg.py", line 512, in run
  File "C:\Users\dst\AppData\Roaming\Build archive\youtube-dl\ytdl-org\tmpjwbwqymm\build\youtube_dl\postprocessor\ffmpeg.py", line 235, in run_ffmpeg_multiple_files
youtube_dl.postprocessor.ffmpeg.FFmpegPostProcessorError: Conversion failed!

Description

After MPD manifest warning, program downloads video and audio from Youtube anyway, but then fails with error message when trying to merge them; this happens on the actual download, and also when retrying, though it correctly does not re-download the parts. Same copy of program has correctly DL'd at least a dozen other things from YT since last update.