Media player, some videos play some turn black after packaging

Hi,
I have several Widget Blueprins with different Media Players- I play a video on widget. I just put media texture in widget, make it material brush and in graph I make event connstruct and then open source and my Media Player and Media texture plugged. For some reason three of them play and three of them turn black in game (after packaging). It dont depend on size of them (the heavier ones played well). They are all Mp4 videos. I’ ve spotted that they dont turn black if i play an image sequence but png sequences tend to be heavy and jpegs don’t meet my quality expectations. Send heeelp!