On only one of my forms - I can't edit fields, can't delete, can't add, can't save

I’m not sure what to do. On only one of my forms it appears to be stuck in some kind of error state. I CAN see it, open it, see the fields, but when I click on any field to edit (or even see the options), it doesn’t expand. NONE of the fields in this form will allow me to edit. I cannot delete fields, either. I double checked and my other forms are working just fine and remain editable. Interestingly, this form is behaving fine from a user standpoint. I just can’t update it. You can see it embedded and functioning here: http://davinciwaldorfschool.org/register-trivia-night/
Thoughts? The only similar things I can find are from around 2012. I am on the latest version. I have tested in Firefox, Chrome and on my phone (Safari) all with the same exact behavior. I could really use some help since I need to update pricing by 4/1. Thank you!

I recommend opening a support ticket for the best assistance: