Hi. I cannot wait for the ticket I have open here… So I managed to direct my problem here.
I have Testimonial custom fields and needed to add photo for it. However, when trying to add new photo the new field already have value “New Field”, “new_field”, “text”. And I cannot modify it also I break the whole entire WordPress Admin. I tried to upgrade the version but still occurred the same issue.
This is the error display in my inspect element:
Uncaught TypeError: Cannot read property 'text' of null
Additionally to my case:
[Deprecation] Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.
Ok, after I enable WP Debug, I saw some of the conflict codes between functions.php and plugins. And this fixed my case.