Hi User_2010 , I usually got this problem with Alcatel. What i do is to check for SDCCH Mean holding time for all of the TRXs ( of course if u’ve got more than One). U could probably see that one TRX have huge SD MHT , then switch off the SDCCH defined on that TRX , you should overcome SD drops. And this TRX might be the cause of your low CSSR because of TCH assignment failures radio. Just try theses , and feedback .
I hope it would help u.