I think the Ibis needs a new rear derailleur. Bike has a new chain, cables, OK chainrings, cogs, but won't hold a gear. Plus the chain is falling off the inside of the 39 going up hill, even after a new BB (old BB was whacked, had that replaced recently, crank set was moving laterally). I think this happened on another bike a few years back; a 7800 derailleur with 20,000+ miles exhibited these symptoms. LBS installed a new unit, *poof* she was good as-a-new. The derailleur spring gets tired. Not unlike male potency issues at my age.

Happily I don't suffer from those, but I do wear out these derailleurs. This one has over 20K miles on it too. LBS's don't see this much, most people don't keep their bikes that long or actually put that many miles on the rear gears. But I'm confident this is the culprit on this bike (the Ibis).

If the spring tension on the derailleur is shot, it can't position the chain at the right angles, and these symptoms would be quite consistent with that. Plus the rear adjuster barrel is just about frozen. That component sees a ton of rain/road salt, so it's hardly surprising.

Not that this 7800 rear derailleur owes me anything after nearly 5 years and probably 25K miles.