Dispensing accuracy

Good day all, My first post here. I have an old Evo 2 that is not dispensing reliably. I needs several flushes in the morning before we get anything near reliable dispensing volumetrics during our QC tests. I have replaced the syringes and the 3 way valves. and completed a recalibration. I am pulling the fixed tips of this afternoon to ensure that there are no issues there. We are using DMSO in this unit. Is there anything else I need to check or replace? Many thanks in advance. Regards Paul T