As you've undoubtedly decided for yourself, this really makes no sense. If the L and S/L have the right voltages (relative to both N & E) at the right times, and you've tried connecting L and S/L to the fan 'both ways around', it really does make sense that it does not work 'as expected', whereas it does on the bench (when you presumably are supply exactly the same voltages to the same terminals.Yes switch live has 230v to earth when on and 0v to earth when off. Timer works fine when testing so I don't think I've fried it.
I find it hard not to conclude that you must be 'missing something' - but goodness knows what! You haven't somehow managed to get the perm L and N connections to the fan swapped, have you (that would probably give the results you are observing)?
Kind Regards, John.