The customer is going to be there this next week, to take a look at his mess. We'll find out then, if Stabil is involved. We are also contacting the tech that did the work, to ask about the tank.
Ethanol must have some sort of corrosive affect (even 10%) or the auto manufactures would not have redesigned the e85 fuel systems. When buying a aftermarket fuel pump some or most will state e85 compatible, I know we are not discussing e85 but it would seem that e10 could have some of the same affects.
Ethanol alone is not corrosive, but as others have said, the additives mixed in with the Ethanol very well could be. In my area most brands of gas adds their own "additive package" that they mix into the raw fuel they receive but because Ethanol is the common denominator, it automatically gets the bad rap. I have a mechanic in my area that has been soaking rubber hoses and small metal parts in a jar of Ethanol for well over 5 or 6 years. It sits right on his sales counter and he welcomes anyone to pull items out of the jar and inspect it for damage. Vodka is composed of two primary ingredients...water and Ethanol. Many facial creams also contain Ethanol and are FDA approved, not that that means anything these days...just saying
Over use Stabil is most likely the culprit. I used the stuff for years in my outboard during winter storage. A little goes a long way but to much will pretty much destroy the fuel system after sitting for a while. I always ran the tank in the boat empty after storage also.