It's hard to tell from the image, but it looks like there may have been some contamination during the manufacturing of the panel, which is causing delamination of the layers.
A solar panel is made up of at least 4 layers of material and relies on a relatively clean assembly area. Not a bunny suit clean area, just one that doesn't have a lot of crap in the air, or contaminants falling off of the assemblers.
In a previous life, I was a manufacturing engineer for solar panels (Transform Solar - company went out of business in 2012) and there were process issues that would cause air to be trapped in between the cells. Those panels were never allowed out of the facility.
From the picture, it looks like the layers are starting to separate where the bubbles are. I wonder if one of the layers had a wrinkle in it, where the assembler accidentally folded the material and then tried to straighten it out. It may have looked ok, but the crease was in the material so the panel failed later. Eventually the panels will fail, but before that, they will become a lot less efficient.
Typical solar panels have a planned life expectancy of 25 years.
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HAM guy (Ke7FIX), Retired Robotics Technician, USAF