I know little or nothing about the strange workings of 406 windows but it
occurs to me that my driver's window often behaved like that, from time to
time, and always had to be 'reprogrammed' by raising it to the fully closed
position and holding the switch 'on' for some five seconds. Recently the
motor packed up and, after changing it, my garage mechanic was very
concerned because it would only move upwards in short bursts and he didn't
know why. However, I held the switch down, as described above, and sure
enough it has been perfectly all right ever since.

However, this seems such a simple and well known solution that I am sure you
will already have tried it, but I offer it just in case!

Eric