JMWE post function execution log shows successful, but it doesn't work

Question

Hello - in my workflow when creating a new issue, I have added a post function to assign the issue to a specific person:

Here is the rule configuration:

When I click into the execution log, it shows the post function was successful:

However, the issue is not updated accordingly:

Christy Kennedy · Accepted Answer

Actually, just found the solution! The assignee was not an "assignable user" in the project permissions.

I am surprised the execution log showed this as a success though...