Reminds me of methanol, only with methanol that only takes a few days. Had no idea E85 did that, must be the metal makeup of that filter. I know aluminum was a big no-no with methanol, everything was stainless.
Is that a paper filter? If so, that's a huge no no with E85. Guys out here just put a teaspoon of Lucas treatment in the tank if it's gonna sit through winter. I always ran a half gallon of cheap pump through the car when I stored it just to make sure. Never had an issue like that. The benefits far outweigh the negatives in my opinion.