Thanks for that tip. According to Lionel, these accessories should be fed 8 to 11 volts; I'm already applying 14v to them (from a fixed voltage tap on a MTH Z1000 transformer). That should be more than enough.
I decided to risk taking the Lionel News Stand accessory apart and discovered some dried-out grease on the pivot gear and on the gear wheel of the "spinning newsboy." I cleaned that off. Also, there were some small roughened areas on some gear wheel teeth -- perhaps enough to cause momentary hesitation in operation. Last night I used an Exacto knife to smooth the roughened places and then applied fresh white lithium grease to the gear. That might be a satisfactory "fix;" however, I ordered some replacement parts for this accessory via eBay. When those parts arrive, I'll install them and check its performance again.
As for the 6-12818 accessory, when I opened it up, I noticed that a mere string wraps around and turns the main drive pulley. Although spring tension is applied to that string, it seems that the string may not get a firm, reliable "grip" on the pulley. Occasional slippage may be the source of its momentary hesitation. If the string has gathered some wayward grease or oil, that might explain the slippage. If so, I'll apply some alcohol to the string for a clean-up.
IMHO, Lionel should have used a rubber belt (instead of a string); it would have more surface contact with the pulley. Better yet, a rubber belt with teeth and a drive gear with mating teeth. Just thinking out loud ...
BTW, I'm sure I'm not the first hobbyist to give an enthusiastic "thumbs up" for your layout. I toyed with the idea of a helix for my home layout, but the geometry seemed quite daunting. With 20/20 hindsight, I should have paid more attention in geometry class.
Mike Mottler LCCA 12394