bestvideo+bestaudio does not always work

[Naomi010Sentzke]

Checklist

• I'm reporting a broken site support issue
• I've verified that I'm running youtube-dl version 2019.09.12.1
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that all URLs and arguments with special characters are properly quoted or escaped
• I've searched the bugtracker for similar bug reports including closed ones
• I've read bugs section in FAQ

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You guys closed my issue as invalid but here are some examples of bestvideo+bestaudio(no other options or slases) failing
https://www.youtube.com/watch?v=PFQa3dHlHSg
bestvideo should be f.137, but it downloads f.248
https://www.youtube.com/watch?v=Fmdb-KmlzD8
bestvideo should be f.315, but it downloads f.399
https://www.youtube.com/watch?v=TkLIovb1qC8
bestvideo should be f.399 but it downloads f.137

I have ffmpeg in path. All the above were in bestvideo+bestaudio(no slashes). And yes this is tested in 2019.09.12.1. bestvideo+bestaudio should download the best.