This is the datasheet I was sent with the steel and I reckon it's about right
It says anneal at 900 oC for 1 hours, cool to 750, hold for 4 hours and allow to cool to RT
1050 oC is hot working temp which is strange that its so much higher than the Annealing temp but Sandvik quote this as the annealing temp....strange
Too high a temp will increase the austenite content and reduce the hardness and wear resistance
Just thinking that these anomalies could be the cause of your HT issues
freezing it can also add a couple of points of Rc