Form processor seems to have stopped adding new contacts
I've just noticed that new contacts are no longer being added to CiviCRM by the Form Processor extension. This seems to be a fairly recent problem - I use it on several sites and all were working OK until a week or two ago, none are working now. No errors are shown on the screen, in server access logs or in CiviCRM logs.
The problem is 100% reproducible even using the "Try out" link in Administer > Automation > Form Processors. The API trace appears normal, with no error messages. I can still add contacts successfully manually (e.g. from Contacts > New Individual) without using the Form Processor.
To reproduce, simply create a simple form processor with a text field to hold an email address. Add action "Contact: Get or create contact by email". Give it a name and include the email field from above. Click the "Try out" link and enter a test email address.
I see a result like this, which is what I would expect:
{ "input": { "email": "test@beeches.it" }, "action": [ { "action": "Create", "output": { "contact_id": 380 } } ] }
When I search for the contact by email or by contact_id I can't find it.
I'm on CiviCRM 5.57.2, Form Processor 1.5.3, WordPress 6.1.1, PHP 8.0.27, Ubuntu 18.04.6
I'm hoping I'm doing something stupid because this problem seems obvious and no-one else is reporting it.