The wheel is set up, and it's been far too long since I've last taken it for a spin - it took me a bit to get it all running smoothly again. Though that is also due to trying the other spindle, which (still) does not work as nicely as the one I usually have.
Why? Well, it would be nice to know... The wheel is always a little wobbly, and depending on how the individual bits are aligned (and they have a tendency to shift a bit during use), the drive band stays on... or not. The "other" spindle has more of a tendency to shift, and there's only one good groove on it, so as soon as the drive band manages to hop out of that groove, it's gone and off completely.
As there's no grooves or higher sides on the rim of the wheel, the drive band will also tend to slip off if the wheel is not well enough aligned. That can happen if the fixing wedge of the wheel support works itself loose, or if the whole thing is leaning a bit to one side and the wheel wanders on its axle, or if it's put on the wrong way around (though it is theoretically symmetrical, it isn't quite).
So. All those are reasons enough to take it out and give it a little test drive before it appears at a demonstration, but the main reason is actually for me to get some practice in... or I will have a very, very tired right arm very quickly otherwise!