You can see that in each section, there is a small hole in the back where you can see the box through the hole. When you buy these, each hole has a pin in it, keeping the ball in the starting area. When you pull the indicator off the backing, the pins come with it. So you only have to keep it upright after you peel the backing off.

Here is a video: https://www.youtube.com/watch?v=TuLClpWRmQ8

You can see that each hole has a red colored pin in it, and you can see the pins come away with the backing (at about 0:21 in the video).

That means the pins could be replaced one at a time to reset the device back to its original "unperturbed" state.

To replace the pins, you'd need to tear the device off of the package. I assume that means cardboard is coming off with it, and the adhesive is ruined for re-application. So now you need to apply new adhesive, and do a good enough job that the recipient doesn't catch on to your shenanigans.

Or you could order your own batch of them and, right before handoff, rip off their sticker and then affix yours to cover the damage.

...which is presumably why these have unique serial numbers! They really did think of everything. (You have to make sure the shipper communicates the serial number to the recipient for that part to function, though.)

You ship them in a box with one sticker applied to the side, of course. #inception

There are little dots at the top of the place where the each ball starts. I expect there is something in those spots which prevents the balls from moving and you remove it before you apply the detector.

I believe those dots above the start area have something pulled out when you take the back of the sticker that stops it from rolling around until it gets applied to the correct thing

You don't, you just flip them all around and jiggle them to reset them. Then you hope nobody does that to your box...

If you don't know, don't guess.

The ones I used (20 years ago?) worked this way. It's not a guess, it's just outdated. Regardless, my apologies for the inaccuracy.

I guess those ones didn't have the 180° sensors on them? With these one it would be pretty much impossible to jiggle both balls into place.

Are you sure? There are holes in the yellow backing that look perfectly placed to have some sort of retaining pin inserted to hold the balls in place until use.

At first I thought they were meant to insert the ball, but the holes look too small.