I have had this happen on a weak tree that was repotted. This tree is still weak in the roots, so I think the tree went into shock because of the root-leaf imbalance in the heat. But budding again is a good thing and it may come through. My tree that dropped its leaves is now healthy. If you have shade cloth I recommend getting it under there and really pull back on the watering. I am using 60% on some of my trees that are weak. Do not let this tree freeze this winter!
I think these need more sun! The leaves look really dark and sparse. You will get better fruiting and growth with more sun.