People have mentioned a prop rod. No need for that ever on AAR/TA cars. Look at your hinges, they have pre-drilled holes in them. Take a round stock think 5/16" bend 2 90's in them. Put these in the holes, will have to measure to get an exact length. But it's much safer & looks better than a "broom handle."
Sorry wished I had pictures to show exactly what I mean, but our TA is gone.
But a great fix to a simple issue.
Thanks, Ken