Well, I got the thing into pieces and found out that the counter-gear is held to the axle of the counting dial by the friction of the dial butting up against the "shoulder" of the gear--if the dial is screwed on tightly enough, it works just fine. If you unscrew the dial from the axle just a little bit, there's no friction between dial and gear, the whole axle will spin inside the gear and the counter mechanism won't show you what's happening on the dial or allow you to start a new roll. Tightening the dial is tricky--the other end of the axle has a slotted head for a screwdriver, but it's hidden beneath another gear. (unless you've got the tools to take the snap-ring off of that gear...) I managed to get a small screwdriver tip into the slot sideways and hold it in place while tightening the counter dial. You could probably hold it with extra-fine needle-nose pliers, too.
I've run a roll of exposed 220 through, and it looks like the spacing is off on a couple of frames. (3&4 overlap, and there's frighteningly little room between 5,6,7.) Not sure if this would be resolved using 120 instead of 220... I suppose there's only one way to find out...
In any case, I'm not impressed by this holder. The price was right, but then I've always been penny wise/pound foolish when it comes to buying gear...