Try 45-60° autosmooth, see documentation https://documentation.beamng.com/modding/modelling/vehicle_modeling/
try not using autosmooth (as you should never use it anyway), instead re-open blender, import the dae from your mod, then see how it looks. If it still looks correct in blender, try selecting the effected verticies, and resetting verticies then after that try setting all required edges to sharp. There's a chance it'll reset all vertices, so you'll have to go around and sharpen everything individually
Or what fillman says though it did look like the artifacts I got from modifying Beam assets without applying autosmooth.
