Toto does not sell seconds. Their quality control is exceptionally high, but certainly it is possible that occasionally something will slip by the inspectors. I don't know what you can do about the seat issue after this much time has passed. As far as the leaking is concerned, I would pull the toilet up and remove the wax rings. Then check the flange (I know it was replaced) Plastic flanges are not the best ones to use, it should have a stainless steel ring. Also, the flange should set on top of the finished floor and be screwed to the sub floor. Examine the wax ring(s) Did the plumber use one or both with the plastic funnel? If so this could be the problem. If the flange is on top of the floor a single wax ring is all that is needed. Two would be too much. Before resetting the toilet, place it over the flange without a wax ring. The toilet should rest on the floor all the way around, and it should not rock. If it is not solid on the floor and/or it rocks, it needs shimming (in the back) Now reset the toilet with a plain standard wax ring. Compress the wax ring with body weight on the toilet, do not use the flange bolts to do this. The flange bolts hold the toilet in place. A properly set toilet does not rock or move at all. One other possibility is a man or boy sometimes has bad aim especially in the middle of the night. This might account for the apparent leak. The toilet should be caulked after installation to prevent urine or spilled water from getting under the toilet. Some places want the caulk 100% around the toilet, other places require the back edge remain open. Your question regarding Toto quality control on toilets made in Vietnam is a good one, but you should know that Toto's quality control is exceptional no matter when the toilet is made, so I would not think it likely this is that problem.