Here is a zipped new 4.15 project with a simple example of it resetting, no matter what ‘Restore State’ is set to - https://drive.google.com/file/d/0B5Hlx38HoC1geDNVVy1KenNGN1E/view?usp=sharing.
I posted a bug report on this here - Sequence Player 'Play' Reset Bug - Cinematics & Media - Unreal Engine Forums - which I have updated with reproduction steps.