Once and a while I will get a drop of ink on that side of a print as the heads start their return back to the right side. For small drops it can be a fuzz or hair collecting ink untill that change of direction of the heads cause the build up ink on the fuzz to drop off. The drop off can happen anywhere on the print as well.
Now for that much ink dropping out on your left side might be the damper not sealing on the head. If you were to remove a damper while the heads were over your print I think you would see the ink run out of that head due to the vaccume no longer being there. So if whats happening is the movement of the head carriage on its way back to the right is enough of a force to have the damper move a bit and let air in for a split second it might cause that larger dropout.
The other thing I have heard is a head that was leaking (inside the head)and the ink would pool inside the head and when the change of direction was made the ink would run out of the head ( from the side ) and drop out.
Going back to what jhilldesigns said about after 30 min the test print is bad and being the damper sounds right as if there is a leak in the damper, as the heads are parked that head will drain out just sitting over the cap tops.