I think there are two possible causes of your problem
1. The transmit power on non-BCCH TRXs is lower than that on the BCCH TRX
2. Too aggressive power control settings.
Case 1 can be corrected by changing the relevant parameters, and case 2 can be corrected by either disabling power control or changing the desired signal level values.
How these changes can be done are very much dependent on your vendor.