https://bugzilla.kernel.org/show_bug.cgi?id=93701
--- Comment #9 from Andy Furniss adf.lists@gmail.com --- Oh, OK, my testcase is a bit different from yours in that I bring up HDMI as a second screen when in X. My symptoms also slightly different in that I get a 2 pix pink line on the left outside display area and 2 pix on right are missing. Maybe different displays behave differently.
I bisected to the same commit as you.