Sounds like it is just using the email of whomever it last sent to, but if you are telling it to scan to Jeff@fakemaildomain.com and hitting send, but Gordan@yourcompany.com is getting it, I would have Xerox send a tech and wipe the device immediately and then set it up from scratch.
But if it just populates the last email you actually chose, just turn off that feature.
Properties > Services > Email > Setup > Security
Or the screen is simply uncalibrated so that the touch points are slightly off, in that case it would be picking the entry above or below the one you choose, if that is the case, get a tech to diagnose/calibrate the touch panel.
