I'm using the latest patch on stand-alone linux server.
In the images above, you will not only see that I'm inside the trader, but you will see the method I used. Use the top catwalk to run and slightly jump to slide in through the opening. The bottom stairway is used to get out quickly.
I hope this is enough information to get the bug report in. Feel free to PM me if you need to use my server as a way to test or replicate the bug. I'd be happy to assist.