Symptoms

Activity line merge does not appear to wait for all lines to complete meaning the Activity that brings all the lines together fire multiple times.
 

Diagnoses

This is a bug in the product

Sample Repro

1. Create a new workflow

2. Add a placeholder with 3 outcomes

3. Add a placeholder at the end of the 3 outcomes

4. Add an email activity and configure the 3 outcomes to go to this activity

5. Select the merge to wait for all previous steps to complete

6. Change the Display Name of placeholder 3 to hang out and change the Display name of the email event to Placeholder3.

7. Run the workflow and note that 3 emails are sent.
 

Resolution

For this case the design was changed to move away from this, but the bug is slated to be addressed in Appit 1.5 update 4 later this year.