If the user no longer has access to the UI_ADMINISTRATION_GENERAL permission, which causes the operation to fail silently. The error is only visible in the browser console, and no alert is displayed in the form.
The error occurs at the request level action=validate.api.exists.

Example 1:

Steps to reproduce:

1. Create a new user named "Test Admin" and assign the Super Admin role.
2. Log in as "Test Admin" in a separate browser window.
3. Open the Regular Expression form.
4. Change the "Test Admin" user's role from Super Admin to Admin.
5. Return to the window where the Regular Expression form is still open for "Test Admin".
6. Click the Update button.

Result:
The update operation fails, but no error message is displayed in the form, only an error in the console.

{     
"code": 0,     
"message": "No permissions to call \"regexp.get\"."
}

Expected:
The user should receive a clear Access Denied error message.

Example 2:

In version 7.4, this can be reproduced when editing an Item. However, in this case, we get "Unexpected server error." instead of "Access Denied".

There may be other places with a similar problem.