Experiment stops when a key is pressed

Hi,
I use win10 and PsychoPy version 1.3
I use videos in my experiment and participant give response to the video with a key -left arrow key or right arrow key. However, when I run the experiment on my computer, if I press any key -left or right- the video stops for a moment, and then it keeps playing. The videos are in mp4 format and it works perfectly in other platforms. Also, I did not use any scripts, I was only using the builder.

Any ideas what could be the problem or how I can solve the problem?