Anxious Tunnel Behavior, revisited

I think I touched on this a few months ago.

Essentially... many dogs are scared of the tunnel. Dogs quickly learn it's okay.

The training plan typically involves one person restraining a dog on one side and the owner calling the dog from the other end of a (usually) scrunched up tunnel. The dog gets treats/play/praise/toys on exiting.

And...if he was worried at all... negative reinforcement was at play. Exiting the tunnel provided some level of relief.

For most dogs, this probably isn't a big deal. They learn to do the tunnel quickly and continue on their careers and that amount of anxiety probably isn't a big deal.

But some populations develop the condition often called "Tunnel sucking" and are magically attracted to tunnels. Sometimes they do the tunnels when not asked (even unintentionally). Sometimes they seek out tunnels. Soemtimes they just seem to have more distance than they've been trained for. Enthusiasm is greater than it should be, even with the high value reinforcers used in training.

Some dogs, either during a lesson or in play, will go through the tunnel a ridiculous number of times. So many that it's silly. They seem happy. But there's a not-so-happy element to it too.

Here's a clip of Luna repeatedly going through the tunnel. Again. And again. While playing with others, but she's also done this in class. In this clip, she had not been in class and I had not reinforced her for the tunnel behavior in over six months.

Is this a normal byproduct of agility training? How common is it? Should we be concerned? Should the anxiety be addressed?

Should we be training and introducing the tunnel a different way?