Everything is happening on Bank 1.

I wonder how responive O2 sensors are if you had a misfire on some ignition sticks the odd time instead of ignition sticks being completely dead to cause a rich reading in the system. I am assuming the fuel injectors are still firing even with a dead ignition stick.

And by the way, a "misfire" is not necessarily an ignition aka an electrical issue. It can be mechanical as well.