Mautic 4.4 API call failures with Fluent Forms

Your software
My Mautic version is:4.4.0
My PHP version is:7.4.3
My Database type and version is:10.3.34-MariaDB

Your problem
My problem is: I’ve been using Fluent Forms for a while, which uses the api to import my contact information from its form data from Wordpress to Mautic. This was working well until I upgraded to Mautic 4.4.0. As soon as I upgraded, the calls to the api started failing. Fluent Forms doesn’t say anything more than that the call failed. If I go back to calling Mautic 4.2.2 (I never installed Mautic 4.3), the api calls work successfully, so the change causing the problem must have been on the Mautic side. I know that it’s not something stupid, like an authentiction failure, because most of my data appears to be getting transferred, despite the failure message.

  1. Is this a known issue?
  2. Where can I find more details about the nature of the failure? Is there a log of this?

These errors are showing in the log:

Steps I have tried to fix the problem: I’ve tested against older Mautic versions, and confirmed that the contact information is transferred properly.