Water header tank is right above there. You may have a leak on one of the pipes attached - there are one or two smallbore plastic pipes as well as the obvious hose. Or it might be venting, blowing off some water. Overfilled? Or maybe an airlock elsewhere due to losses from those o-rings? Cap not sealing right?
Get the o-rings sorted, and the system carefully refilled and bled as necessary, then see if the drip is still there.
Good luck, Ross K
