Inspired by this question, I have a similar but somehow different problem.
I recently assumed a tenure-track position. One of my strategies for a visible start is to have a strong presence in social media. We have a youtube channel in which students regularly explain their achievements. Or sometimes we post short educational materials. We also prepare brief videos for each publication as some publishers promote the videos.
However, one of my PhD students refuse to cooperate. I specifically asked him in the interview (both video chat and email questionnaire) if he is willing and ready to prepare such video materials for the group, and he firmly answered YES. Now, he claims it is not part of the job description for a PhD.
I first preferred to ignore this conflict, but now other students are reluctant to do so. Now it is more a matter of my authority.
Since I am new, I do not want to take the case to the department head or other officials.