path unbalance (not imbalance… is it ?) means that you have a faulty hardware that adds losses to the radio propagation, in one direction.
For instance, one combiner is faulty => loss in the DL direction = tx unbalance.
or the rxdiv of the TRX is faulty => loss in the UL direction = rx unbalance.
other problems can be feeders, connectors, duplexers, jumpers, antennas, …