Matinee Data cannot save actors to groups?

Hello everyone! I am creating a matinee with a matinee data file instead of the default matinee InterpData. I am experiencing trouble when attempting to create a matinee that uses this matinee data. When I open the matinee using my data, I must assign a camera and an actor in the scene, which I do; they appear in the “group actors” tab of their respective groups. However, if I close the matinee (be it to play the level or any other reason), the matinee forgets I had assigned actors to the group. This means that the camera I had assigned is forgotten (and the default game camera takes over) and the actors I made move with the matinee don’t move anymore. However, the fade track on the director group still works just fine, which means the matinee is playing, but the actors that I was trying to animate aren’t linked to the matinee…
I’m sure I’m missing something obvious. I just can’t seem to find much documentation on the use of matinee data files (apart from 2 or 3 questions in the answerhub…), so if anyone can point me towards anything that might help me I’d really appreciate it!