What is going on with my derailleur?
I see no way for the pictured setup to occur while riding.


The silver bushing is bolted or rivetted to the cage plates
Cage plates are contiguous plates of steel with no gaps
Lower jockey wheel is also bolted to chain plates.


These three items form a box through which the chain runs.  No amount of folding or flipping the chain would get it out of that box.

The only options I can think of are


Someone misassembled the chain in the first place - Plausible because the chain is low tension at that point, and you may not notice the clattering.  I've personally ridden with a group ride up a gravel track and someone else only noticed the same problem halfway up (hi Brendon!)
Notice the scarring on that bushing - the chain has been running on it for a while.
Someone has fiddled with your chain while the bike is out of your sight. Unlikely because its a dirty business messing with chains and that's a long way to go for a joke


If your chain has a quicklink then fixing is easy and can be done roadsize with pliers, or some people can split them by hand.



Opinion  If the bushing is only attached on one side. then its not doing you a lot of good.  Consider removing it completely and see how things go.  Store the small part, in case it gets worse and you need to refit it later.