I need to investigate a non working leccy window in one of my SDIs. It suddenly started working a few months ago on a day when it was below freezing the whole day. Then ceased again once it warmed up a bit. I have a hunch that the anti fingertrapping 'system' is based on an over-current sensor that measures the excess current before the top stop is reached. And if it is, chances are that by changing a 5p resistor or something could set the current to a different level (to compensate for friction and wear).