Not being able to see it is a small part of the problem. The jamming is sudden, and first, one of us pushes the other person's legs. Then I have to balance the bike while not being able to propel it, and I may not even be able to turn the cranks into the stepping-off position. That position is usually with the left pedal down and my right foot disengaged and reaching for the ground. So not being able to move forward and not being able to stop leaves me with nothing to do. The last time this happened, I managed to stick my right foot out, but the road was heavily sloped downward to the right, and putting my foot down tipped the bike over to the right. I don't remember, but I might have had to jump off and put two feet down. And remember, I'm balancing for both of us. My wife isn't heavy, but I don't have strong arms.

For the time being, my wife has asked me not to risk that shift, which limits our gear range.

I just got a wacky idea. How about putting the big ring in the middle position and then just having two rings? They would be 28 and 54. The front derailleur might or might not be able to make such big shifts.