I experienced the same problem in version DCS 2.9.1.48111 beta. I tried disabling secondary shadows (and changed Cloud details from Ultra to High, but I do not suppose it is relevant) and then reloaded the mission. Sadly the ABRIS map was still flickering, so I gave up and came here to report the problem. Then I started up DCS again to check whether the problem comes up on other maps/mission too, and eventually learned that now everything seems to be in order again (no flickering ABRIS). So maybe disabling the secondary shadows and restarting DCS can fix the problem for others too.