Thank you GoPhoenix for your idea. I just now gave the front arm a push as my wife closed the awning and it closed without leaving any gap at the top of the arm.

Before closing the awning, I lightly tightened the knobs on both arm assemblies to help assure that they moved directly up toward the back channels. (In the past I would always leave the knobs open fairly loosely.) I did my best to keep the arm assemblies lined up while pushing straight up on the front arm.
We're going to be in the Santa Cruz Redwoods RV park for two weeks starting next Monday, so I'm very happy to get this to work at least on this last attempt.
I talked to a person at Dometic earlier this morning and was advised that the awning could unfurl while driving if we couldn't get the awning fully closed.
--Bruce