mp4 video streaming: fast start up, but gets stuck...

[ST]

Hello,

I have two mp4 files served by nginx: A ( https://goo.gl/lYGXjC ) and B
( https://goo.gl/ZsnX7M ). File A starts pretty fast ca. 2s and it
buffers/caches "future" content, however to B it takes more than 6s and
it doesn't seem to buffer/cache. However A gets stuck periodically which
makes it impossible to view (probably when it fails to cache), while B
plays nicely all the time. Here are my questions: 1. What makes A start
up so fast? 2. Is it possible to have both - fast start AND stable
playing? I have not encoded neither of the files but here is the ffmpeg
-i output of both ( http://pastebin.com/SuwYZkWP ) and AtomicParsley -T
of A ( http://pastebin.com/GRWJkqNy ) and B
( http://pastebin.com/YGq0HjCU ). If you need any additional
information, please, let me know.

Thank you very much!
ST