I've seen this happen on low mileage engines when an air clear wasn't seated/sealed properly. All that dirty air getting sucked into the engine is like sandpaper on the cylinder walls. I'm not saying that's the case here, onlythat I've seen it happen. And although your timing chain is metal, the gears are only nylon and if they wear enough, the chain will jump a tooth. I look forward to your weekend update!

 

I've had that happen to a 1994 Plymonth Acclaim. The timing chain had jumped. Needless to say, the engine had some high mileage and too much play that could have been the cause.