I've read that the Chinese vendors are no longer making production runs of parts only for purchase by the US train companies. That instead, they have to order extra items of the finished product and then disassemble them for parts. So I guess that must be true. I don't believe it was like this when Sanda Kan was the major train vendor/manufacturer in China. I could be wrong on that, but parts for common items were certainly more readily available years ago.
Even more disheartening, is that this is a larger production run item aimed at a larger audience than some of the high end items. That it is both "obsolete" and "unavailable" is not very encouraging for anyone considering a LionChief plus locomotive purchase.
It could also be that the "formula" of the plastic has changed. As an example, I've got rolling stock from the MPC period of Lionel, where the plastic knuckle couplers still spring open when activated. I've got more recent production Lionel cars where the plastic knuckle couplers no longer spring open. They do open, but they don't spring open as my MPC era cars still do.
Heck, I've got plenty of lower-end types of locomotives with plastic gears that don't have all the latest electronic/digital features, but I've never encountered a problem with any of the plastic gears on them like this one here.