Comment # 7 on bug 1001473 from Thomas Bechtold

(In reply to Dominique Leuenberger from comment #6)
> Is this still an issue? I have since upgraded to a 4k display (yay!) and
> screen recording worked (tested with GNOME 3.28.0, TW snapshot 20180314)

It is still broken for me (3 displays, 1600x900 and 1920x1080 and 2560x1440)