You are lucky the noise stopped with that tiny piece of hair taken out…. I have had roombas for 22 years… I have 7 of them. And I clean mine every week because I have 4 cats… they ALWAYS have hair caught between the brush and where it screws in… (where you took yours out) that has NEVER been any bother to the function of my roombas…. My loud scratching noise is usually the tire mechanism or I need to clean and oil the motor.