C# wpf questions about mediaelement

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C#

WPF

I would like to ask you the following questions about MediaelEment;

I'm arranging 8 of MediaElement using WPF.
When I played some movies of MP4 at the same time, some of 8 MediaElements doesn't work.
I would like to work 8 MediaElements at the same time.

Please teach me how to work 8 MediaElements at the same time or reduces program processing.

Otherwise, Please teach me If there is the other method (not to use MediaElement )

What I have tried:

I try to do below program ;

I'm arranging 8 of MediaElement using c# WPF.
I try to play some movies of MP4 at the same time.
But, some of them don't work.
I would like to work 8 MediaElements at the same time.