I think this is what progress looks like:

Lamb #721 is still getting out of the electronet enclosure, but in all previous instances, Cass would find him and spook him sufficiently that he would charge back into the ‘net to rejoin his mates.  In the process, he’d get himself hopelessly tangled in the fence and would usually pull down a long section of it with his struggles, often leading to more escapes.  This morning Cass noticed him before I did, and when I saw them she was calmly holding him against the ‘net.  Cass tends to be a bit gonzo around the sheep, a good trait if she needs to move 120 hard-headed ewes that have never met her, but less good with small groups or single nervous animals.  The best border collies learn how to modulate the pressure they exert to control their sheep without alarming them into flight.  I’m hoping this is a sign that Cass is starting to learn the lesson.