Don't know the one in the 106, but the tilt/slide ones I had on a 405 and
306 both had drains in each front corner. The pipe runs down the inside of
the front pillar.
Try a bit of stiff wire.

Is the roof tight fit when shut?it might just need a little ajusting
here and there.

I had the same problem with my 98 405 water was leaking through the light, i
found out i was not closing the sunroof properly, it looked shut from the top
of car but had to push button just a little more to close it properly., i had
not long had the car so was not familiar with the roof any chance you have
done the same thing?