Maybe it is the extreme heat, but the plastic cording must stretch causing the lens to fall out. This is not something I can pop back in and be done with. That is, I’d put the lens back into place, but the lens falls out again.
This happened to me twice. First, in San Salvador at the beginning of September and again in Panama City on December 22 when the glasses are almost exactly a year old. (I believe each lens has now fallen out.)
Luckily in both cities, I have found that there is amazing reciprocity amongst the eyeglass stores. In each city, the first optician shop I walked into repaired my frames free of charge! Each time, with just a few words and a fast look at the situation, the plastic band has been fully replaced.