Check your “call set up indication success rate”.It is poor due to t3101 expiry.Now,after each T3101 expiry,RACh retry takes place upto MAXRET.So,each of the attempts gets added in the denominator,which makes the RA303I value small.
You can increase the “RACH Min. Access level”,”RACH Busy threshold”,& “RACH error threshold” to reduce this,but you cant eliminate the effect totally.
It is better if you use “Immediate assignment commands/Immediate Assignment requests” in place of RA303I.
Hope you got the point