My housemate bought a spinning bike since all fitness places are closed due to corona. It has an ordinary (non-road/mtb) saddle which creaks when pressure is applied on its edges (nose, back, left/right). The sound appears to originate from the saddle rails itself.
We've tried replacing it with another saddle, but the sound remains. We've tried taping the rails, hoping to reduce metal to metal contact, but the sound remains.
How can I reduce the creaking sound of the saddle? I've included a picture of the saddle below: