One of these trees died a miserable death and I am wondering if the root system is the cause or at least part of it? I enclose pictures too.
If I buy another tree with roots like these can I do anything about it before planting it?
Oh man . . . horrible roots that never grew out of the plug stage. Those plants were likely dead on arrival. With understock like that, the grafts never had a chance. The odds of a plant surviving long term with roots like that are extremely slim.
I recommend showing these pictures to the grower. You deserve replacement or full refund.