Intake coolant leak
It does leak internally a little as well. Fortunately I have never let it leak long enough to get more coolant inside except for the lifter galley, I will change oil before running.
I did buy a borescope and ran it down the water passage, definitely mismatched inside and pushed gasket up. That's why I think slightly thicker headgaskets will help by giving a little more space at the bottom of the V where the intake and head meet