After several trials I encounter this must be a serious bug:
Case: Woodelf + 5 ranged accuracy, marksman + 5 accuracy ranged weapons
Attacking the same enemy from a static postition by quick reloading, in two of three cases I don´t get +10 accuracy but only +5.
There are + 5 randomly leaking.
I tried it several times from several static postitions.
I guess the marksman talent is triggered randomly.