I've found that early PS1's (and at least one other brand of traditional electronic reversing unit I've encountered) are particularly sensitive to minimum voltage. When you move the throttle to zero in order to leave reset there must be very near zero volts at the track. You shouldn't have a problem if you're using a KW but it's worth a check.
At least one of my units with PS1 (early model) will only leave reset occasionally, and it's directly related to this. Most of the later ones, if not all, leave reset correctly every time.
Nonzero-volts-when-throttle-off is most frequently a problem with several types of electronic transformers, Powermasters, etc. and normally not with traditional transformers.
Additionally I've found that in some of these situations all that's necessary to ensure zero volts at zero throttle is to place another load on the track in addition to the locomotive, perhaps a lighted passenger car or caboose, particularly if it employs traditional lamps rather than LEDs. In these cases it will ensure that voltage is dragged down to zero as the throttle is closed.
Mike
