We have had great service over 25 years from 6 Velux roof lights BUT
now one has a leak in one lower corner. I wonder who else may have
had & solved a leak.

It is difficult to discuss because of the technique they use to build
these, but I have used clear sealant all round the actual window
glass, I have used same at lower end of aluminium rail running down
each side.

I can see the drips coming off a draught-proofing strip which runs/is
channelled horizontally along the lower end of the wooden window frame
- not the outside casing.

I cannot where this water in entering the window system.

Any clues ?

Thanks