i don’t know the nokia equipment, but i think you should focus on the following :
external cell definition in OMC-R
cell definition in MSC
LAC definition in MSC
If the OMC-R is okay, then the problem must come from the MSC’s. Double check both MSC’s, there MUST be something wrongly defined.
You can also investigate the QoS counters in BSS and NSS, to see where is the failure occuring exactly.