Cannot interact with previously created sidebars

I am using the custom sidebars widget to serve different custom menus depending on the page. Recently, the sidebars widget area became unresponsive and I can't modify anything anymore.

The entire right-side area for Appearance > Widgets is just inert and nonfunctional. Both the Custom Sidebars that I made and the Theme Sidebars (Using Magazine Premium) show up but they are inert and nothing happens. I can't click the little arrow to pop-down the editing, nothing. For some weird reason, the FIRST menu is still editable but everything is totally unclickable and unresponsive. I dearly need to edit these menus again. I recently upgraded to Custom sidebars pro to see if it would fix it, but it didn't.

I get two errors when I try to inspect the element:

The first is 'Uncaught TypeError: undefined is not a function' and the second is
'Failed to load resource: net::ERR_CACHE_MISS'