This can be pathloss issue, please check the CQI / SRS which UE reports, maybe from SRS you can calculate the pathloss and UL received power. This maybe the problem which leads to less power reception in UL data at ENB. ENB should command UE to use its max power to transmit the data. This can be done using TPC MAC command. UE also can report its power headroom report to ENB to calculate UE's transmit power.