Symptoms

A duplicate task action field is created when using an existing field in a section. Using the existing Task Action field in the InfoPath Client Event wizard generates a prompt asking if you want to bind the control to a drop-down list, even if the existing control is a drop-down list. Selecting "Yes" creates the additional field outside the section, which gets re-added after manual removal.
 

Diagnoses

This is a known issue that currently has no fix.

 

Resolution

A workaround is to hide the duplicate field.