It sounds like more than a brake issue if you're right. I'd call tennis machines back assuming that is where you got it. Is this a new or reconditioned machine? All you should need to send them is the crank tensioner assembly and not the whole machine.
When you're dead you don't know you're dead. It's the same way when you're stupid.
Balance - 31.0 cm, Weight - 358 g, SW - 346 Kgcm^2