This is a InfoPath 2010 filler form on SharePoint 2010. Recently upgraded to Office 2013 (from 2010).
The form was working fine when opened in InfoPath 2010. Now that we got the upgrade, opening the form in InfoPath 2013 causes issues (but It is still a InfoPath 2010 form filler).
The person picker field seems to be the root of the bug. It is unresponsive for many users. At first, it was unresponsive for me but all of a sudden it seems to work now after seemingly not having changed anything. However, it is still unresponsive for other users.
What could be causing this? What changed behind the functionality of the people picker in 2013 from 2010?