When you have a people picker hosted within a SmartForm via a Sharepoint list, the behavior of the picker control varies depending on who gets selected.
For example: if there is more than one user that has the same first name, and you choose to specify the first name within the form or view you will see that this will bring back multiple users as opposed to just the one.
This shows when multiple users with the same name get selected. In this instance there are two users with the name Anthony, so if selected, both names appear within the picker selection:
You may see on some occasions if you choose to keep the picker empty on the form in runtime, and click enter you will see multiple users being returned here:
This has been identified as a bug and will be addressed within a future release of K2.
The workaround for the time being will be to change the original rule:
On the create button rule the execute action should be the following:
“then load picker list control cache with data”.
With this the picker should work as expected in runtime mode on the form and in SharePoint as well.