Limited Collector's Edition Class J Side Rod Issues

[J3AGreenbrier614]

I just received a Limited Collector's Edition Class J 4-8-4 #608. I was told it was a great runner from a family member who previously owned it and gave it to me. I sat it down on a long section straight track to test it out running in forward and reverse. She runs fine in reverse but when she moves forward, the rearmost side rod twists upward and locks up. I'm not sure what to do about this and I don't have the funds to order a newer J to take its place and thought I'd ask what should I do

Please provide feedback.

J3AGreenbrier614