Jira Workflow Toolbox Create Issue post function not passing on values in transition screen

Hello!

I'm trying to setup a create issue post function using JWT, The way my transition works is it's an any to all transition that pops up a screen for user input, that input is then used in the create issue post function that creates the issue in a different project under a parent set by a parser expression.

Now the above screenshot works,

However, the way I had it set before (and all of my other create issue post functions coming in from a DC migration) is instead of parser expression for the Active Billing and Ongoing Billing Start Date fields, I was doing "Field in current issue", and selecting the same field. However I kept getting validation errors in the JWT audit log that those two fields are required (which they are in the field schema for the target issue type, but I was supplying them in the transition screen that pops up with this transition)

My question is, do I need to change all of my create issue post functions that rely on a transition screen to use a parser expression instead of "field in current issue"?

Am I doing something wrong with "field in current issue" that I need to fix instead of using parser expression?

Thank you all in advance.

Pierre Ibrahim