Video of the experiment pause when the participant press a key


I use win10 and PsychoPy version 1.3. I add videos in mp4 format to the Builder. Videos work perfect normally. However, when I run the experiment and press a key video pause for a second. Since we interested in the perception of the participants, even the little durations in the videos affect the results.

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