Intricacies with OIC XSLT Mapper

Summary:

We have an OIC integration that calls Concur REST API to do user provisioning and de-provisioning. I run into an issue that doesn't make sense at all during "rehiring logic".
There is a PATCH Operation that we can call to "re-activated" user account in Concur.

In POSTMAN client, it worked just fine.

Sample Payload of Request Body (in POSTMAN)

Here is my OIC Mapper and Yes I have tried many different combination of passing "null" values to the terminationDate Schema. (Including explicitly setting null as the value)

For unknown reasons, when I execute this OIC integration (Screenshot because the formatting on this is horrifying), following error message is throwing on Concur side.