Thank you very much! Some of this article's comments were helpful too. That's one of the few articles I've seen that say anything negative about Peruvian avocados. In addition to the ripening problem, the article confirms that the taste is inferior to Californian/Mexican avies and the skin is thick & tough.
There are many web sites touting Peruvian avocado production and their farms. Widespread bad-mouthing of Peruvian avocados would negatively impact this growing industry. Surely Costco and Sam's Club are getting some negative feedback about them. The last bag of Peruvians I bought from Sam's Club ripened so unevenly that I cut all of them in half, took a photo and used it to get a full refund.
Both Costco and Sam's Club switch to Peruvian avocados around June every year, presumably when the last avocado crop from California and Mexico has been consumed. The entirety of Peru is located in the southern hemisphere, so their seasons are reversed, as are their avocado harvest times, so Peruvian farms can provide avocados when sources in the northern hemisphere cannot.
Worldwide demand for avocados all year round has increased over the past few years -- Thus the Peruvian solution. For the sake of the Peruvian avocado farmers, I hope the uneven ripening problem can be solved. Maybe, as you suggested, the so-called uneven ripening is attributable to a fungus, which could be a solvable problem. Until it's solved, I'll stick to avocados from the northern hemisphere.
Postscript: Life is pretty good when you have the time to complain about southern vs. northern hemisphere avocados! And I just found some Mexican avies at Target for $1 each.