Problems with Api V8 on create relationship for a meeting with user

Hello to everyone,
I have a problem when I try to create events on meeting module, and then create a relationship with user. So the record will insert into meeting_users table and then it is possible to show events on shared calendar.

We create a meeting using apiV8 (our suitecrm version is 7.11.2) after create, we invoke the method to add relationship for the new meeting with user, and the api returns ok message, but really, the relationship isn’t created.

Has anyone else had the same problem?