Checklist formatter is not loading correctly on the form and the OOB UI Macros "inline_checklist_macro" and "checklist_template" have not been modified in any way:
The Checklist formatter is controlled through Angular technology, which is provided with ServiceNow. However, often times customers will attempt to import different versions of the Angular library through a UI Script. This is advised against by ServiceNow Support as it can lead to issues such as this.
Remove the script which is importing the external Angular library. Run a query against sys_ui_script where "script contains angular".
If this doesn't resolve your issue, here is another cause of the same issue