InfoPath Dev

Hi, i've an infopath 2010 form with three people picker that allow multiple values.

When the form is submitted the first time the submit goes fine.

When a user open again the form and try to submit the form throw a validation error indicating that the people control doesn't allow multiple values.

The only way to overcome this issue that i've found is remove the people control, and insert expression that shows the selected users.

This is a known bug? There's a workaround to fix this behaviour?

A clarification: the issue occurs only with infopath forms, not with infopath client.

Thanks in advance. 

PeoplePicker has a setting/property that allows multiple selections. What's this set to in your form?

 What do you mean by this?: "the issue occurs only with infopath forms, not with infopath client."

Does it happen in the browser, or the client, or both?

Sorry, I just cannot reproduce this.

I'm attaching my form. It's simple, but I was able to select multiple people in each picker, submit, reopen, add people, submit, etc.