Thx for the details rachid,
Well, I’m not a nokia expert, but perhaps you should check your parameters : it’s possible that you push MS too much in the inner segment ? MS will suffer poor RXLEV, and fail to seize the TCH.
Second possibility, which happen a lot in case of dualband cells : swap feeders… the inner segment of cell A is actually transmitting on the antenna of cell B…
Other than that, I leave it to nokia experts 🙂