Usually when yokes fail, they fail at the sharp winding bends.
And they leave a sign - usually a black mark or missing insulation.
Since you aren't reading the horizontal, I'd look hard at where the horizontal winding gets terminated. It may have separated there.
I'm don't see any blowouts, but the picture is from one face of the yoke, so flip it and take more pictures so we can see what is going on or not.