ESA Back Payments

I received ESA back payments from 2014-2018 as I was moved from Incapacity Benefit onto Contribution Based ESA, today I received a letter saying they would call me reference my late husband who passed away in February 2015 and think they owe him the above from 2012-2015,I had to ring them as they had our old telephone number and whilst speaking thought I would ask about myself as I only got back dated to 2014, because they switched me to Income Related in January 2018 all my computer records were re-started hence nothing prior to January 2018!! I am now due to receive a phone call from them within 24 hours so they can check my paper history. My point being - all of you who received back dated money to 2014 please check they have your computerised records or you may dip out on the other 2 years they owe you, and if your spouse died before 2016 and was in receipt of Contribution based ESA if you haven't received a letter from the DWP, ring them up.