I've seen bizarre stuff going on with the ZMF-II clocks. I've never seen or used a tap'n'set (a couple of people have them, but they had the *pushbutton* one), but I know already that on the ZMF-II, if you very slowly move your finger to the sensor, it won't activate it. You have to do a rather normal movement. What's even more bizarre is that if you hold your finger on one sensor (which activates the other player once as it should), but keep your finger on it, when you press the second player's sensor, it will switch back to the first. This is proper behavior and happens also on the Chronos (button and sensor). But if you release press the second player sensor again, while keeping your finger on the first sensor, it then SWITCHES BACK to the second player! And then the first. And then the second. This is very abnormal behavior.
Even more bizarre, if you put the ZMF-II in your lap, it does not do this at all! It just switches once (as expected) just like a chronos, and then goes back to the player originally holding their finger on the button and stays there while the second sensor is being mashed. I don't know if it's the sensors they used with detecting things nowhere close to the sensor, or some absurd firmware bug, but that's insane.
I saw this mentioned somewhere by someone else, but he claimed that the "button" version does not exhibit this, so it had to be referencing the tap and set version (as no button ZMF-II exists).
I just got the TAP N SET clock. It is a little bit difficult to set up because the instructions are not very clear. That’s not the problem. The main problem is many many times when you touch the sensor to stop your clock and start your opponent’s clock it does not work. Sometimes it does it when you touch it many times you have to touch it multiple times to get it to change. That is no good in a tournament. Especially if you are playing blitz. Wasting many seconds every time you make a move is awful during blitz games. I tried it at one tournament and I am returning it. Don’t waste your money