What do you think about this?

[attachment=0]Aaa Hah moment.jpg[/attachment]

Looks to me like the water was following the grove in the slate and being redirected too close to the headlap.

Missing Slate

Yeah, both slate were culls, but somebody nailed them down anyway. Go figure~ :shock:
Any roofer would have set them aside for something other than field slate, They’d go in my ‘hip’ pile first.
Two inch headlap on this roof. Took me a while to figure out what was leaking since the one I pulled wasn’t broke.