CSSR in CS Domains

How we can improve KPI 2G & 3G Call setup Success Rate from MSS level?

from the troubleshooting we got the top failure is CM Service Abort Times ( when user ends the call during setup time) , user behavior.

CSSR calculated by the below formula
CSSR=( MO Assignment Success Times (times)+MT Assignment Success Times (times))/(MT Paging Response Times (times)+MO CM Service Request Times (times))*100

Your suggestions and feedback formula in order to optimize it is highly appreciated
The vendor is Huawei.

Admin note: this post was updated with image below.
CSSR in CS Domains causes

Hi experts,

What is your suggestions to improve Call setup success rate KPI from CS core for Huawei from 98.3 to 98.5 or more?

What are the top 5 call setup failure causes?

CSSR in CS Domains causes