Direct3D output

[Serval]

Hello all,

I'm having this strange problem lately and hopefully you can suggest how to solve it: from time to time I edit videos, splitting and joining. And usually everything works just fine. But sometimes when I do everything exactly the same way when I open the joined video in VLC immediately Direct3D output window opens and I see two videos playing at the same time. The first one and the joined part.

The videos have the same type, frame size and frame rate. And still some are being played OK and some within two windows with Direct3D output.

What could be the problem?

PS: in other video players everything works fine, but VLC is the best for me.

Thanks a lot in advance!