In the UP link, UE Sends MSGs to Node B, which is capable of Detecting the UE for paging/Signaling puposes. However, the problem arises if hardware is Not functioning well, i.e TRXs or Combiner/Duplexer, Also check that the power is surficient enough in the system…BADICM(Cause effect) can also be one though brought by the Power incerficiency.
I hope that will help. thanks.