I always tried to shoot for temperature stability, If your zone temperature is set too cold, you will start with cold rollers and the temperature will increase throughout the run, If your chilled water is too cold, any metal parts that the water goes through may sweat, causing water to get into unwanted places.
I suggest setting the zone control at 75-80 degrees F and chilled water a little colder at 60-65 to start with, the zone control is there to keep the inker at the same temperature whether it is a cold startup or continuing a long run.
You may have to adjust the chilled water temperature to achieve the desired temperature stability.
Also your ink supplier should be able to give you some more specific numbers for ideal temperatures, If you have a zone control for each inker, ask for numbers on specific inks / colors as well.
If your chiller unit is giving you problems, one of the first things to check is the condenser(s), and the condenser fan. The condenser looks like a car radiator and the fan pulls the air through it, if it is clogged with dirt / spray powder, or whatever and the airflow through it is down, the refrigeration will not work as efficiently.
Hope this helps,
press on