TMS320F28069: The Pos_mrev variable is updated too slowly

I am going to do the motor deceleration measures, but I find that the variable at this position st_obj [Motor2] .vel.conv.Pos_mrev is a bit slow to update, at least greater than 500ms, and I will use this variable to calculate the current position. I use It is an incremental encoder. Our product is used to pull the motor with a rope. When the load is large enough, I let go. The recovery force of the motor will be greater than the set load torque, and I want to The torque of the motor is given a value of 0 to make him brake, but my test found that because the st_obj [Motor2] .vel.conv.Pos_mrev variable is updated too slowly and the test result is catastrophic, is there any good way to solve this problem?