The flexing wires soldered to pivotting trucks was, in fact, the weak point of these things.
Other than that, considering the price and the time, they were pretty good power. They ran allright, but at the time, they were considered very good runners. It is important to remember that when these appeared, only Kato had the type of power chassis that has now become the standard. Kato was considered the El Expensivo manufacturer, back then.
LL did keep the same chassis, but both the BL-2 and the FA-2 did have shells much improved over the ol' FP-Whatever.
These things make good cheater boxcars. The locomotive will pull every piece of rolling stock that you own up a fifty per-cent grade on a seven inch curve.