I doubt it's an error but let's assume it is. When I look at an online calculator for fat loss which uses some standard formulas for BMR (google fatcalc) I see

I doubt it's an error but let's assume it is. When I look at an online calculator for fat loss which uses some standard formulas for BMR (google fatcalc) I see that losing 62.5kg (91 pounds) means your "calories to maintain" are 1000kcal lower than at your starting weight. It takes less calories to maintain a lighter body. Nothing surprising here. Metabolism didn't "slow down".