u/Cool_Confection_4357

Just joined the reddit and im not that much into the Train Simulator fixes and so on, i recently got the MSTS conversions mod, but all the 4-8-4 conversions are broken (Miwakee Road 261, UP FEF-3 & ATSF Northern), if they go on flat or downhill rails, they start to bump and derail, yet they don't do that on uphills, is there any reason or solution to this that anyone knows? I'd really apreciate the help, thx and sorry for the hour, still wish u have a good night