Hello Amir,
Do you have cooled water temperature monitoring and non condensable temperature? Look for big difference between those temperature each street since air leakage will decrease non condensible temperature even more than usual. As a rule of thumb, gap should be around 5 C. After locating the street in trouble, shutdown the fan and monitor with an IR camera how the cold area stars increasing, if there are one. It could help you to find the leakage.
Best,
Manuel
