First several observations about my EL U33C: The first one I opened at my LHS also did not have a yellow stripe on one side; the second one did. Has anyone noticed that the "gang planks" at each end swing up? It is fast becoming my favorite new loco.
That said, even though the couplers appear to open all the way, it's not enough to uncouple from the cars. I remember another post somewhere about some one else noticing this on their's, but I understood the problem to be they just weren't opening. Mine open, but not enough.