I ended up rolling the dice on another milk car after returning the defective one to Trainworld (they made me eat the shipping...). I got another B&M from Charles Ro and it does not derail like the defective Trainworld car did. The couplers don't work with other Lionel cars but no surprise there. Also, one of the sideframes was bent up and had to be massaged back into place. Just happy the thing tracks properly and doesn't derail over every switch.