The two relays provide power (phase) to the damper's "open" and "close" pins.
When the "open" relay is activated, the damper opens correctly.
The issue is that when both relays are open, the damper unexpectedly closes. This suggests that a current or phase connection is being made to the 'close' pin even when it should be disconnected.
so this “leakage” current is suffcient to move the damper…