Bonsai Nut
Nuttier than your average Nut
I am surprised. You mentioned in a post recently that you live closer to the coast which provides the moisture in the air that we miss in the central valley. Pines love the heat and will grow good looking foliage and seem to thrive, but moisture laden air is missing which the needles prefer. Weak lower branches is common though I have no idea about the grafts. people have told me that grafted trees will sometimes live for years and then for some reason the graft union gives up.
For now I am putting it down to "user error". I believe I waited too long on the cork barks to repot them, and they were a little weak last summer (which is why I knew I needed to repot NOW no more procrastinating). And then I moved too aggressively.
The ones that suprised me were the yatsubusas. These are prolific black pines and bud back stronger than any cultivar with which I am familiar. Of the two that I repotted in early December they both crashed - HARD. One still has a few needles and buds so I am hoping I MAY be able to save it. The other is in a landfill. I have two new yatsubusa that I purchased and then repotted in early January. They look awesome. Not a single sign that they were ever repotted.