Yeah, I would use the built in COMOffset if I were you. Changing a center of mass on a model/mesh is really for if it’s a simple enabled physics model. I wouldn’t be so surprised if Epic’s built-in vehicle class completely negates/ignores the center of value functions you were using to change it, so there would be no conflicts with the vehicle simulated-physics of their class. While I think cars are also integrated with PhysX to a degree, they kind of should be treated as their own unique thing due to how the wheels, torque, and suspension are simulated by the class which is behavior not built into a default free physics object. E.G. if you just attached models of wheels to a box using physX constraints, it may somewhat roll but certainly not handle like you would expect in the real-world, which is why PhysX itself has its own specific implementations of wheel behavior that Epic’s Vehicle Class uses.
A lot of arcade games with vehicles don’t even use “precise” wheel simulations, and just raycast down where each wheel’s suspension would be to figure out where to place the wheel model and how much force to apply in the opposite direction based on raycast length in order to keep the vehicles main chassis/simple physics body upright (technically hovering if you paid no attention to the illusion of the placement of the wheel model). Although Epic’s Vehicle class aims towards realistically-simulated physics, so if you can get that to handle how you want it to behave and it doesn’t require anything fancy like being able to dynamically place wheels in-game like in Kerbal Space Program, I’d probably stick with it.
A possible method for debugging your center of mass if it’s indeed not debugging, is just adding a debug component like the EnviroIcon thing, have it not hidden ingame, and just do a set world location of component to center of mass in the tick. Again, because vehicles are a class of their own, I’d recommend seeing if the vehicle class has a different node/function for getting the center of mass from the vehicle class instead of the generic get center of mass from mesh.
Best of luck!