Another new client in Dunblane has some leaks in his shed, the likely reason was that water was blowned in underneath the felt.
Solution: a little bit of Sitcks Like Sh*t did the trick!
One can see in the picture below the water clearly coming up the shallow slanted roof and into the ceiling. With severe Gales and heavy rain it actually looks quite well sealed, but not enough clearly. Adding the strong adhesive “Sticks like Sh*t” into the build and all should be good.