Assuming that your team members switch Mandarin due to habit, start a practice of taking notes during the team meetings on the major points discussed in English

Assuming that your team members switch Mandarin due to habit, start a practice of taking notes during the team meetings on the major points discussed in English. If you take up the role yourself all team members would have to present what is discussed in English to you. You might miss out on banter or smaller discussions during meetings, but anything directly related to the project would be clear to you. This might not work out smoothly at first, but as long as you have the role of a note taker, the team would be more aware of your existence.