I think they have recently redesigned the rating and checkbox elements, as I have created a custom extension which uses them and they have also both stopped working.

I am having this exact same problem. I have a project dashboard in Page Designer with about 10 (5 dot) rating fields that worked fine for the past 6 months.  Yesterday I changed the color of the dots and tried to edit layout in Page Designer.  Had multiple "page will not load" "try refreshing" errors in Page Designer. Finally gave up.  Today, Page Designer loaded but none of the rating dots are visible.  The field box is still there but no content.  I tried deleting and replacing them, changing colors, checked layer order...nothing is working. 

 so I think I am having this issue too - previously my forms have displayed tickboxes and today there are none showing. how frustrating!

Same here - no checkboxes content displayed in Page Designer

Same here - no check marks showing up in page designer.  I submitted a ticket late last week without response yet. Anyone else hear anything on this issue?

On Friday AM I received an e-mail from Airtable support that said:

There is an issue/bug that happened with page designer that started yesterday afternoon that has impacted checkboxes and ratings. As a next step, I'm going to reach out to my team lead to take a deeper look at what may be going on here. 

As soon as we've had the opportunity to connect, one of us will follow up with an update and next steps. Thanks for your patience while our team investigates this issue further. 

So at least we know it's a recognized issue.