hei zoy….
Do you remember my 1st case which i have discuss with PIX…??
try my steps to solved your SD problem..
1. identify the TRX UPlink & Down link Quality. if their has bad quality, you may check all of the TRX connection cable till to antennas system and make sure their properly connected.
2. if the SDCCH channel available on the bad TRX, try to move it into better TRX. it will help you to reduce SDDrop.