flickering secondary monitor since the Intel update.

details: a 4K screen next to a 1080p one. it goes black for a moment, comes back, someitmes teh windows jump to the main screen. ive rebooted plnety. id love a checklist rather than random tips, since Ive already tried random tips :) i have about an hour tonight to test things, and i would rather go through them in a sensible order xD tell me what you would check first and i will report back with results. what am i doing wrong??

