Hello all, I really hope someone will be able to help.

My Kent (probably) mango tree is mature, if small, and for years has yielded delicious fruit. For the last 3 years, we see an increasing occurrence of what what I assume to be mango internal decomposition - AKA jelly seed. The fruit center develop a jelly like texture, but even worse, a sour, fermented flavor. The fruit outer most side is tasty as always. This seems to develop before picking the fruit, and the sourness increases with time if is is left after harvest. The more colorful side of the fruits (they are mostly green when ripe) tends to be in a worse state.

As said, this has started about 3 years ago in a few fruits, and now I rarely find un infected fruits. We have a very warm mediterranean climate, with this summer being quite harsh. There was also an incredible amount of fruit flies this year, but we sprayed the fruits and had none infected with maggots.

The tree suffers a little from leaf rust, I will spray it with copper based antifungal soon after harvest.

Can it be the effect of extreme heat, or perhaps the fruit is infected with fungi? Can fruit fly "stinging" (I know that's laying and not stinging) transfer pathogens?

Any suggestion will be greatly appreciated.
Shai