You need to check overshooting of the cell and contain the coverage by tilting and also reducing Access Min Parameters (Depends on Vendor) ussually ACCMIN parameter (Cell level ) is set -110 and if you minimise to -102 or -100 dbm it will rediuce the overshooting.
Remember it is a trade off you will improve the coverage but reduce the traffic.
Otherwise install TMA (Tower Mounted Amplifire to improve UL coverage