Image freezes on videos

At two recent meetings I launched, one of the participants has the image frozen in the videos I show (part of the presentation). The audio still works but the video image freezes. It only happens to him with the videos, because the rest of the presentation does not give him problems. Also, the other participants have no problem and the recording of the meeting shows no freezing. I don't know if it is a matter of the signal of origin (mine) or a problem of the participant with its reception. What can I suggest to him?