Missing permission on adding registrant to webinar

I inherited an app with scopes webinar:write, webinar:read, user:read that manages registrations to webinars. When adding a webinar registrant (webinarRegistrantCreate) for at least one webinars host I’m getting error code 200 Invalid access token, does not contain permissions:[User:Edit].

I cannot find anything pointing why this permission might be needed. Before I force my users to refresh the token, I would like to at least understand why do I need this. Any help?