you know its funny, I know the metric system and what it means when i hear 20C outside and how to dress, but when the outdoor temp if given in F, I have no friggin idea what it means lol. So when it comes to troubleshooting chillers i need the pressures in PSIG and the temperatures in F.
I would check the accuracy of the transducers and is the chiller short cycling? I know as well the dishcharge muffler they have been having problems with and the oil filter could be partial plugged, I am running into the same issue and changing the oil filter and maximizing the off cycle time that has taken care of the intermittent oil failure. But I have also had a problem with the oil float wiring and I ended up replacing the cable and problem solved (again intermittent). I would look at when your oil float is open or closed when the other circuit is running.
I hope this helps somewhat
from your fellow british colony eh