I'm experiencing the same behavior, but only when use the "Original Quality" optimization preset or a quality equal to or better than the original. If I choose the "Optimize for Mobile" preset it works as expected. I'm running the latest beta PMS (Version 1.14.1.5488) on a Synology NAS. 

Whenever i try to optimize a video file Plex acts like the optimization had no errors but the optimization happens instantly and there's no files created. 

My management area for optimized files shows the one i attempted to create but i can't access it from any apps, likely because the optimization failed and there's no actual optimized file to stream. 

Anyone run into this issue? I'm running the server on a basic Windows 10 laptop and Plex is the latest version.

Optimize feature not creating files