I would expect the Get recently updated and created contacts | Contacts API endpoint to return any changes made on a contact even if the the property change is a custom property. I have tested it out on my own portal by changing a custom multiple check box property and when using the Get recently updated and created contacts | Contacts API endpoint and appending the &property={{internal value of the multiple checkbox property}}, I’m able to see that the contact was returned in the response.
In this case, to help further troubleshoot this, could you share with me your:
1. Portal ID
2. The contact id that has recently been updated
3. The custom property that was updated on the contact record and didn’t get reflected on the endpoint
When paging through the following endpoint: Get recently updated and created contacts | Contacts API, contact 14010201 was returned in the JSON response with the cf_notiz property changed to ‘test’. Let me DM you the parameter I used with the offset value.