SP2013 Enterprise, InfoPath 2013
I've built a form using InfoPath 2013 for a SharePoint 2013 list that includes two people picker controls for entering domain users. The fields these controls are bound to are just basic "Person or Group" fields.
The problem is that when any user filling out the form types a name into the picker, if they hit "Enter" to check the name it spits out a red error message below the control saying "The target [very long jumble of characters that includes the control name] for the callback could not be found or did not implement ICallbackEventHandler." But if the user then clicks anywhere on the form, the picker successfully checks the name and clears the message.
The form submits properly, but obviously we can't have the users seeing this nasty looking error message. I've done my research and the only instances of this online are of people making webparts by code, and the solutions don't apply to InfoPath.
I have tried completely deleting the fields from the list and form and recreating them from scratch but with the same result. This type of setup has worked perfectly in the past, the only difference I can see is that in this case is that the people pickers are not on the default view of the form, they have to be accessed by a button that switches to their respective views. I don't see how that could matter, but it's the only thing I can think of.
Does anyone know how to fix this error in InfoPath? Or at least can shed some light on the cause?
Edit: Per Diego's answer I have ensured the columns are set to pick people from all users, instead of from a group.