Update: Per Northrop Grumman, this is debris from an "acoustic blanket". Possible that it came from inside the fairing, where it would have been used to shield Cygnus from noise & vibrations during launch. Probably got snagged on the array when the fairing separated.
Here's a look inside the Antares fairing that protects Cygnus during launch, complete with mylar blankets. This could be the material that became jammed in the array. Image credit: @ken_kremer