Sorry for a late reply. Steam locos definitely have proven different physical running characteristics. The main one is Draw Bar height, relative to the Driver centerline. Too low, the load is physically leveraging the forward Drivers up, causing loss of traction. There is an article/forum post somewhere years past.
And make sure that all Drivers have some vertical movement allowance so as to independently lift/lower the centerline. With crowns and dips in the rails, you’ll loose traction if they all can be in contact. However, too much can also result in same as Drivers aren’t heavy (unless gearing is adding).
This was noticed in N and seriously in Z but easily resolved with brass front boiler inserts.