First of all, thanks for the answer/attention.
Well, I made a lot of testing today and find out this only happens with the Streams from my App.
Following your suggestion, I created a new UWP App with a MediaElement and a Player Framework Players, and two buttons (whose functions were to set the same source to both Players). I used the BigBuckBunny Smooth Stream from your Xaml Samples App, and a Stream
from my App.
Using Fiddler I verified that with BigBuckBunny Stream I got two manifest requests (one for each Player as expected) except the first play-through (the same I experienced before with Xaml Samples App). With my Stream I got four (two for each Player) everytime
I set the Players source.
I made some more testing using my App and your Xaml Samples App. I injected BigBuckBunny Stream on my App and except the first time I always got only one manifest request (the same behavior). Injecting my Stream on Xaml Samples App I got always two manifest
I don't know why, but with my Streams I get every single time two manifest requests. A Fiddler capture is present in the following
(this capture is made with the UWP App I created were a MediaElement and a PlayerFramework Players load the same source simultaneous)