Again: Ethanol does absorb water. If it absorbs a lot it separates out and sinks to the bottom just like water. Isopropanol is much less prone to do this.
the 10% ethanol is there to make it driveable, and a gallon of 93% could be helpful, as it did for me. But, if it never did this from 10yrs back when ethanol was introduced, it could be a sensor of some kind. have you taken it to a dealer?