The alingment with the sun light may solve partially the problem, but… with the day/night cycle, at 12:00 hours, the light are aligned with all the vertical surfaces and the problem appears again.
I’m thinking about modify progresivelly the shadow bias from 0.02 to 0.05, from 10 to 12 hours, and return to 0.02 until 14 hours. With the vertical light, the 0.05 bias are good. Will be a bias multiplier, so the user still can set the absolute bias value in the menus.