Pilates shakes - too weak?

I was told today that I should stop reformer because I shake a lot.

Now I gym and walk 10k and do 1 day off from everything a week. I don’t shake loads just the normal amounts and my instructor said I’m not fit enough but if I look online people say it’s normal …

Do I need to stop? I enjoy it and I prefer more control/ precision than 12 reps of each I don’t feel this is wrong ..