Water may be arriving from higher up
A split slate, damaged felt or leaking gutter joint can keep one area of timber wet.
Old felt can sag behind the fascia
When this happens it may collect water and tip it against the back of the board.
Check the rafter ends
If the fascia is being removed, look at the timber behind it before fitting a new board.
Want the problem checked properly?
If you have a photograph from safe ground, include one that shows the whole area rather than only a close-up.
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