We had very similar experience with medical bill (insurance didn't pay, we moved, years later found unpaid bill on our credit report). Collector offered to pay

We had very similar experience with medical bill (insurance didn't pay, we moved, years later found unpaid bill on our credit report). Collector offered to pay and clean up the records. After going through some doubts (what if collector lie about clean up?) we did pay and within weeks credit score returned back.