There is possible bug in version 1.0.3 with client side "Concatenate".
Steps to recreate:
1. Create action with concatenate with at least two text inputs (f.e. "Text1" and "Text2") and without <Separator>
2. Watch its exit ( using debug or set field on your pane)
3. Concatenate returns "Text1nullText2" (shoud return "Text1Text2")
use this acion inside "Service" to force tersus to use server side concatenate.
For best results, use the Firefox browser..