Three years ago, a mango grove owner called me to look at his grove, much of which was producing poorly. He was especially disappointed in a block of several rows of Orange Sherbit, in the ground several years, each tree over 15-feet tall and wide, and healthy looking. Most OS had produced nothing, and the remaining OS, almost nothing.
When they mentioned that they had been spraying insecticide to kill Sri Lanka Weevils, I recommended that they stop. Two reasons: the weevils were causing only minor cosmetic damage, and the insecticide was killing off pollinators (especially flies).
I also recommended fertilizers and nutritional and fungicidal sprays to use.
In 2020, production reportedly (I didn't visit in season) increased on the other varieties, but not a bit on Orange Sherbet. Same this year.
In 2015 I was hired for just that Summer, to pick the experimental mango grove of Zill High Performance Plants. I picked the original Orange Sherbet tree, and also a very large Orange Sherbet produced by top-work grafting on an old tree. Both were highly productive. They were surrounded by hundreds of other mango varieties.
I have heard reports of other individual, productive Orange Sherbet trees, surrounded by other varieties. At the grove with a problem, there ARE other varieties in the same field, but....
At this year's "Mango Summit", Dr. Alan Chambers, of the Tropical Research and Extension Center (TREC) in Homestead, reported on genetic research done on the 200 plus varieties of mango at that research station. When he studied the genetics of many seeds from those trees, he found that many varieties had produced large numbers of selfs, while others had produced almost no selfs, instead favoring outcrosses. Some of these, that favored pollen other than their own, were also picky about which other variety of pollen that was accepted.