Sorry for the long story, hard to describe what happened. Weird issue riding yesterday, hoping some mystical gurus here can provide input. About 15 min into my ride during a hard pedal uphill, my chain (without any shifter input) did the old 'kerchunk' and went into a different gear. When I got to the top of the hill I shifted a few times in either direction and it felt fine, so I kept pedaling. During a downhill, however, I noticed quite a bit of chain noise/slap which was odd because the derailleur has a clutch and there weren't that many bumps. I slowed down and pedaled around for a bit on a flat area to see what was going on. No obvious issues, got off the bike and checked alignment, seemed fine. Tried to move the derailleur around with my hand and it was snug, clutch worked fine too. When I pedaled backwards, however, I noticed the chain got really slack and flopped all over (normally it just moves in reverse and the amount of slack doesn't change). I started riding again and there didn't seem to be any issues going straight on flat and level. Going downhill again, more chain slap, so I got off the bike and checked things again. Still didn't see anything obvious, so I shifted through the gears in both directions and tried riding again. No issues for the rest of the ride going up or down. Chalk it up to a momentary glitch? Or is it a possible sign of an impending failure? Thanks in advance.