Thanks to both VegasTriker and BlazingPedals, Both of your responses pointed to the chain tube, which the mechanics at my bike shop
had not bothered to inspect. Your emails guided me to inspect the chain tube on my wife's Catrike Villager. Low and behold, what do I
find? The rear strap which holds the chain tube to the frame had gotten torn loose in the sweater fiasco and that's why the chain was
leaning rightward: the chain tube had come loose and was hanging down at the rear. Voila!
The mechanics at my local shop missed it. But my compatriates on bikeforums.net led me right to the problem. I will order the parts
to repair. I just knew something wasn't right with that chain
!
Thanks for your expertise,
Scubaquarius