Yesterday, I got the bright idea to ask for his formal retrieves again. Well, what showed up was the fact he hadn't done it in so long that he lost the position for bringing it back. While trying to get him to line up and come close enough for me to take the dumbbell from him without having to reach too far, the whole behavior just about fell apart!
He would go get it, but bringing it back ended up triggering a wide array of really strange stuff I never seen him do even when first learning this. He would wonder around then come back, take the dumbbell and carry it off somewhere, then put it down and get it again. He wouldn't get it even at times without being told to get it.
It was terrible. You'd think we never worked on this before. Breaking it down more, I could see that the trouble was truly with the "Front" position, which is where he ends up after bringing the dumbbell back - or at least ideally, this is where he should end up. So it's now back to drilling fronts in order to get it nailed down again and trying to incorporate fronts more often.
And it's just fronts. The "finish" position is fine (most of the time), probably because it get used more often (it's the same position as sitting at heel that he uses if we stop while walking).
Fronts are just something I don't call for or need very often. There aren't too many times I need him to sit right in front of me.
For skills like this, I will have to remember to formally work them so that they don't fade.
Chalk it up to another lesson learned!