When riding my vintage bike with a Campagnolo crank and Origin 8 chainrings, I have noticed from time to time when I drop the chain from the big to small chainring, usually just before a climb, the chain will not engage the small chainrings and skip over the top of the chainring. The skipping will continue until I stop the cranks and coast momentarily and the chain will drop into the teeth. The chain I am using is an 8 speed SRAM chain. This happens maybe once every tow or three rides, so it's not a big deal, I'm just wondering if it's the nature of the beast or can something be tweaked to stop the skipping.