Hydronic system support

Boomba

Hello, I’m new to hydronic heating and the house we purchased a couple years ago is boiler heated in floor slab hydronic. The system itself is 25 years old. It’s split into 5 zones. The question I have is we put in a new boiler last year as the previous was going and I’ve noticed zones getting heat when all thermostats are off(usually only 1 zone letting heat through)I should note the circ pump is in line before the zones and I wondering if the pressure from the pump Is forcing some leakage through some of the zone valves. I’ve also noted that one zone valve is mounted upside down but the flow indicator is right on the zone body.

Before I call a plumber in I’d like to do some work myself. 

hot_rod

So pics
or a hand sketch would help to see where the ghost flow is causing over heating.