If a new action is created (e.g. by inserting keyframes), the header was not garuanteed to display the right action. Notifiers were fine here, redraw took place, the editors action was just not set soon enough for the drawing. Now make sure this is set correctly by ensuring the animation context is right (same as the other editor regions do before drawing). Maniphest Tasks: T86809 Differential Revision: https://developer.blender.org/D10796