iPhone asks for passcode for a reset, but no passcode is set
My wife and I just got new phones and I've been working on clearing out our old phones. Mine went without a hitch, however I'm at the very end of clearing my wife's phone out. When I attempt to erase it via "Erase All Content and Settings", the iPhone asks me for a passcode, even though there is no passcode currently set for the phone.
I've tried all known passcode(mine and hers), however I'm at 11 attempts, I'm getting tired of waiting for 60 minutes for another attempt.
Is this passcode different than the phone passcode? Will erasing with iTunes via "Restore iPhone" cause any issues? What's the best way to proceed?
[additional information: The phone was originally set up using my apple ID account. When my wife finally set up her own apple ID we switched it to her account.]
Thanks for any suggestions.