FERS Debt to the Government

Wondering if anyone has experience with this. I was contacted by HR stating that I was incorrectly placed in FERS RAE with a 3.1% mandatory retirement contribution instead of the FERS-FRAE with a 4.4% mandatory retirement contribution back in November 2015. My current debt to make up the difference is $14,756. I'm meeting with HR and payroll to discuss options but prior to the meeting I was wondering if anyone had a similar experience and what the outcome was. I've read a waiver can be submitted if it was an administrative error and there is no evidence of fraud. Thank you in advance.