Can't save any changes on the Content Language & Translation page

I’m using Drupal 8 and when I go to /admin/config/regional/content-language and try to turn on “Custom menu link”, it doesn’t save, and it just reloads unchecked.

I saw here that you need to check the actual items, as well, to get it to save, but that doesn’t work either:…

Then I realized that I can’t save ANY changes to this page.

I see the warning “(* unsupported) Paragraphs fields do not support translation. See the online documentation.”, which was red, before I turned off translation for all Paragraph fields, and then the warning turned orange. I had to go to the actual Content Type edit page to turn off translation from paragraph fields to get those changes to save.

Nothing is saving and I’m not seeing anything in the dblog. It just reloads as it was. I’m not even sure where to start on this. Any help would be greatly appreciated.

Drupal version: