Old Mutual repeatedly avoids paying out to Deceased Estate Beneficiaries

My wife had two Fixed Deposits with Old Mutual - both of which matured in January this year. She died in December 2018, leaving me as her sole beneficiary. Old Mutual paid out the smaller of the two within 6 months. And they have been avoiding paying the other ever since, despite the fact that my lawyer has gone in to see them 3 times and made numerous phone calls. She has now reported Old Mutual to the banking ombudsman. There is NO excuse for this behavior - which is making it impossible for me to wind up her estate, nearly a year later.