Huawei NRT ISHO Success rate

[kyokuman]

Hi,

I have quite bad ISHO NRT success rate from 3G to 2G.

I am checking this counters and values are quite high :
Number of Timeouts of Waiting for IU RELEASE COMMAND Messages During Outgoing Inter-RAT PS Handovers Initiated by the RNC (Cell)

Do you know which timer is related to it? When does it start and expire?

I imagine it start when RNC sends CCO request to Ue.
And expire if RNC doesnt receive Iu release command from CN.

However, I couldnt find the timer itself. Which parameter is it?

Thanks for your help