The paper presents a procedure for increasing the quality of results of the Distribution State Estimator (DSE) integrated into the Advanced Distribution Management System (ADMS). The basis of the presented procedure is the DSE tuning process which is defined by business goals and the desired level of the DSE results quality. Verification of the presented procedure was performed on the real-world example of SA Power Networks' unbalanced distribution power grid. The paper addresses the challenges and learnings in the period 2019-2021, methodologies for rapid detection and mitigation of data issues, mechanisms for monitoring and maintaining the quality of DSE and the benefits that the company achieved by increasing the quality of DSE results. The presented procedure can be applied to any (un)balanced radial and weakly meshed distribution power grids with (a)symmetric state.