Cubase using a lot of storage while running

Hi ! I’m currently working on a big orchestral project with no audio files, everything is MIDI. While working on it I saw that the SSD drive the project is stored on was full although it’s not supposed to be. I couldn’t even save the project anymore. I made enough space to save and then closed Cubase. While closing the project the drive also went back to its “normal” remaining space. Nothing particularly strange you could say. “Just make some space on your drive”. But, Cubase was using around 65Go of space ! What for ? Why so much space ? Can I prevent that from happening ?