I use rubber cement (lightly and just dabs) on the bottoms to hold the felts. It's easy to remove if needed. I would first let the machine air out before doing anything. Then determine if the case is the cause or the machine or both.
I would also ask your friend if was serviced before you received it and see what she says! She may not know it wasn't cleaned up and have her husband do it for free. I would hint at that since you paid a premium for the machine.