I'm having the same problem, but not with ore cars; boxcars.
Recently received 3 RMT U.S. Navy box cars from Pat's Trains. On all three of them the roof walkway isn't secure and one it was totally loose inside the plastic clam shell. I contact Pat's Trains and he suggested I contact RMT - which I did (and cc'd Pat's Trains). Before I could get a reply from RMT, Pat's Trains sent me a label to send them back for repair (with my eye sight it's had to glue small things down).
I also received the Hennig's Trains anniversary boxcar manufactured by RMT. Couplers don't work at all! They are supposed to be sending me a return label to send it back so they can fix it.
I also had to send back to Mr. Muffins an RMT Soo Line Soo Locks anniversary boxcar. Same problem - couplers don't work. They are stuck closed (tried briefly to open them, but concerned I might break them while doing so).
I am concerned because I have quite a few more RMT rolling stock on pre-order. While I'm getting good response from the dealers I'm buying from, it's a hassled to have to take them to a shipping store to return.
