Invalid custom field update by post function results in misleading "Couldn't create the issue" message

Issue Summary

If a user creates a post function on the Create transition to update the Team field but puts the value as the team's name instead of the expected UUId, this will result in the issue failing to create with a generic UI error message:

 

Couldn't create the issue
We're having some trouble creating the issue
Refresh the page and try again

Steps to Reproduce

1. On the Create transition of a company-managed workflow, select Update Issue Custom Field from the Add Post Function screen.
2. Select Add.
3. From the Issue Custom Field dropdown, ** select Team.
4. For Custom Field Value add a team name (instead of the correct UUID)
5. Publish the workflow and attempt to create an issue. Observe generic UI error. 
6. In the network panel observe error "Error server response: 500"

Expected Results

Accurate error message describing the problem that needs fixing.

Actual Results

Inaccurate error message indicates this could be a temporary error rather than something that requires reconfiguration of the workflow.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available. For issues like this we recommend creating a Support Ticket with us and be sure to provide a link to the project on which you are seeing the error, and a screenshot of the error.