looking for some advice. I have some new to me MTH streamliner passenger cars. All of the cars have couplers that will open but not close without pulling the pin to let them close. They will not of course function on the layout as you cannot couple the cars together in a normal manner. This is my first experience with the MTH streamliners. All my other passenger cars are Madison heavy weights and I have never seen any have this issue. I have two separate packs of streamliner cars and all six have this same problem. Any advice on how to fix these (besides going with Kadee which is on my list to do).