Thank you for the information and your question. I am a little befuddled that the State would allow a dispute
/appeal by the employer at this late date. Although it is not unusual for the State to allow some leeway (like a few weeks or even a few months), several months is very unusual. If I were you, I would consider hiring a local employment law
attorney who handles unemployment issues to handle this. Your strongest argument is that the appeal/dispute by the employer should not be heard since they missed their appeal deadline by months. I can say that usually,unless the employer has "good cause" to show why they delayed so long, the hearing officer will find in the claimant's favor.
Even if you do have to go through this, remember that it is the employer that must prove that you intentionally, or through gross negligence, did whatever they said you did. It doesn't sound like they could do that, even if the hearing officer gives them a chance to do so.
If, by a very long shot, the state would find for the employer, you should easily be able to get a waiver for repayment of the benefits based on the delay and a hardship.
Please let me know if you need any clarification. I would be glad to assist you further if I can.