Keep in mind the Prewar 265E motor was designed nearly 90 years ago to work and run on normal tinplate track and it does that flawlessly. Whether or not correctly functioning prewar Commodore has trouble over Fastrack switches or not, I really can't comment on, but IT's probably fair to presume that Fastrack wasn't necessarily designed to specfically work well with Lionel prewar locos. You have to keep in mind, clearances, and flange depths were a little different in those days. That said, most of the time the problem boils down to center rail contact gap distance in the switch compared to the loco pickup. The other thing that can and does come into play is on a 85-90 year old motor, the roller pins tend to wear and elngate the holes in the the collector bracket. In addition, they can get very gummed up. So much so that you could have only one roller really functioning, and that there could be your problem.