World/Scenario editor not working on third party routes

[ATSF3814]

This is a really odd problem I've started having lately. On RSC routes or routes that I get through Steam, (Ohio Steel, Fort Kent) I can use the editors just fine. But on third party routes (NS AND, Willamete Pass), I can only use the scenario editor once. If I place any locomotives or rolling stock and save the changes, I can't go back into the world or scenario editors. If I try to, Railworks immediately crashes with a Something Bad Has Happened error.

The only way I can fix the problem is to completely remove the route and reinstall it but then the problem just happens all over again. Verifying my cache doesn't seem to help at all. Any ideas?

[Machinist]

Did you try placing default (buit-in) rolling stock? One cause of SBHH and crashes is missing textures, or blueprint (flyout on upper right corner) unduly unchecked after you loaded the editor. Another day, in a test scenario, I had some SD70s placed with the blueprint pack checked, once I was placing Dash 9s to play I unchecked the SD70 blueprint but forgot to delete one of the SD70s, which crashed many times the game until I realised what was wrong.

[ATSF3814]

I placed some Dash 9s and SD70s but I know I didn't uncheck the boxes.