Hello Sergiu,
The issue could be your video card ram and the quality of the video or it could be something else unknown to me. The tutorial videos player has been updated to use YouTube embeds now so that the quality of the videos and bit rate can be more easily adjusted. Adjusting the quality of the video to a lower level should help reduce some of these issues you are experiencing with playback. You’ll have to find a happy medium between quality and what your machine is able to cleanly play.
Abraham