Tribunal decision being overturned

Hi
I won my case in court with dwp (who did not attend)
I am now waiting to hear from the dwp regarding my new amended award.
I telephoned them yesterday and was told it was with a decision maker !!?? Is it possible they can overturn what a judge and doctor say I have been awarded!!!?? If so this is surely more stress and anxiety and if a decision has been made from a court of law how can they overturn it without even being at the court in the first place?? Has this happened before??
Looking forward to your reply. 
Many thanks for any information