Japanese plum tree question

Hello,

We have a loquat tree (Japanese plum tree) in our garden which at the moment is giving us a bumper crop. However the tree was brutalized by an excavator driver some years ago during some excavations for the laying of pipes in the garden - many branches had their bark torn out by the excavator, requiring a massive application of grafting paste to cover the gashes up and avoid disease. However my mother insist that, despite the bumper crop, the tree is not well as many fruit are "diseased" while still in the tree and unmature. Does this mean anything or is this normal for this kind of tree?

Cheers Nicholas

 

There are two huge Loquat trees on the lane in front of my house. I always think the fruit looks diseased!