If you are using the original a.bog0 and a.bog1 points on the model, the answer is "Yes" the mesh is preventing it.
What I had to do when I put out the Undec RSD4/5 kit is make an attachment mesh for the RS3 body that had the about the same data as the original a.bog0 and a.bog1 points, but on the a.bog1 point, I had to rotate the z axis attachment point 180 degrees to get the correct orientation of the truck and mark it as reversed in the config so that the wheels would rotate in the proper direction (Obviously I adjusted the bogie attachment points fore and aft a bit to get the correct spacing).
The reverse box will only change the direction of the wheel rotation.
The reason it was done this way is because it is the same truck under both ends. This way you only need to have 1 truck on your hard drive instead of two.
I can offer a couple of solutions...
1. You can make your own attachment mesh using PEV's attachment maker and make up a attachment mesh with the bogie points with the correct orientation and make the necessary entries needed in the config file.
2. You can download the Undec RSD4 or RSD 5 from the DLS and copy the attachment mesh and relevant entries from that unit's config file and copy them into yours.
3. Download the Undec RSD 4 / RSD 5 from the DLS, clone it, and place your artwork on it. The graphics files for the Gumbytrains RS-3 and the RSD4/5 are the same.
The RSD 4 and 5's come in 2 versions, one with roller bearings, one with friction bearings.
RSD 4 Friction
https://www.auran.com/TRS2004/DLS_viewasset.php?AssetID=251515
RSD 4 Roller
https://www.auran.com/TRS2004/DLS_viewasset.php?AssetID=251516
RSD 5 Friction
https://www.auran.com/TRS2004/DLS_viewasset.php?AssetID=251517
RSD 5 Roller
https://www.auran.com/TRS2004/DLS_viewasset.php?AssetID=251518
Hope that helps!