Letter of overpayment on 4.5 year old claim?

So I just woke up to two nice new letters from ESD. They're claiming that the week of August 6, 2016, I failed to meet job requirements and as such owe them money. Yes.. a week 4.5 YEARS ago. Luckily I have a great big book of all my job search stuff and it looks like I went to 3 workshops that week. I'm just stunned though how/why they are going back that far to try and get repayments. Am curious if anyone else is going through this.