Start with the standard trolley scenario: trolley is heading towards five innocent people but you can redirect it towards one. Suppose you think that it is wrong to redirect. Now add to the case the following: You're restrained in the control booth, and the button that redirects the trolley is very sensitive, so if you breathe a single breath over the next 20 seconds, the trolley will be redirected towards the one person.
To breathe or not to breathe, that is the question. If you breathe, you redirect. Suppose you hold your breath, thinking that redirecting is wrong. Why are you holding your breath, then? To keep the trolley away from the one person. But by holding your breath, you're also keeping the trolley on course towards the five. If in the original case it was wrong to redirect the trolley towards the one, why isn't it wrong to hold your breath so as to keep the trolley on course towards the five? So perhaps you need to breathe. But if you breathe, your breathing redirects the trolley, and you thought that was wrong.
I suppose the intuition behind not redirecting in the original case is a killing vs. letting die intuition: By redirecting, you kill the one. By not redirecting, you let the five die, but you don't kill them. However, when the redirection is controlled by the wonky button, things perhaps change. For perhaps holding one's breath is a positive action, and not just a refraining. So in the wonky button version, holding one's breath is killing, while breathing is letting die. So perhaps the person who thinks it's wrong to redirect in the original case can consistently say that in the breath case, it's obligatory to breathe and redirect.
But things aren't so simple. It's true that normally breathing is automatic, and that it is the holding of one's breath rather than the breathing that is a positive action. But if lives hung on it, you'd no doubt become extremely conscious of your breathing. So conscious, I suspect, that every breath would be a positive decision. So to breathe would then be a positive action. And so if redirecting in the original case is wrong, it's wrong to breathe in this case. Yet holding one's breath is generally a decision, too, a positive action. So now it's looking like in the breath-activated case, whatever happens, you do a positive action, and so you kill in both cases. It's better to kill one rather than killing five, so you should breathe.
But this approach makes what is right and wrong depend too much on your habits. Suppose that you have been trained for rescue operations by a utilitarian organization, so that it became second nature to you to redirect trolleys towards the smaller number of people. But now you've come to realize that utilitarianism is false, and you haven't been convinced by the Double Effect arguments for redirecting trolleys. Still, your instincts remain. You see the trolley, and you have an instinct to redirect. You would have to stop yourself from it. But stopping yourself is a positive action, just as holding your breath is. So by stopping yourself, you'd be killing the five. And by letting yourself go, you'd be killing the one. So by the above reasoning, you should let yourself go. Yet, surely, whether you should redirect or not doesn't depend on which action is more ingrained in you.
Where is this heading? Well, I think it's a roundabout reductio ad absurdum of the idea that you shouldn't redirect. The view that you should redirect is much more stable until such tweaks. If, on the other hand, you say in the original case that you should redirect, then you can say the same thing about all the other cases.
I think the above line of thought should make one suspicious of other cases where people want to employ the distinction between killing and letting-die. (Perhaps instead one should employ Double Effect or the distinction between ordinary and extraordinary means of sustenance.)