Snapped a chain in half on my last ride. Replaced chain. Everything went to hell. I've readjusted everything to get it shifting smoothly again. I also removed 4 links from a 116 link chain to get the proper length.
I would venture to say there is not 1000 miles on the cassette and chainrings. They don't appear worn. The cassette in particular still looks good.
When I stand and apply moderate heavy load to the cranks, chain slips and jumps like crazy on almost every pedal stroke that I push hard.
Chain slips on every front chainring and is worst on cogs 5-8 of 8 (smallest cogs).
I'm reasonably savvy with these types of issues, but I cannot figure out what the hell is going on.