Told I owe money back on my benefits after 10 years as a medical assistant

After 8 weeks of benefits I got a notice saying I must repay some of it. I worked as a medical assistant before this. I did not notice any errors at the time. Has anyone disputed one of these?

Thanks for writing this out. I went through something close to it last year, and it settled down once I kept a simple log of every call and form.