All Forms broken from Squarespace's API

We have noticed this week that Squarespace's form handling API has broken which silently killed all of our forms being able to submit. (This manifests as the Submit button changing to Submitting... and then never changing again. In the console, a 400 error is visible from /api/form/SaveFormSubmission.)

Does anyone have any experience mitigating this? Our forms are vital to our marketing and having silent failures is not an option. In our case, our forms end up in our CRM and I'm considering custom-writing the forms to not use Squarespace's API handler. I'm wondering if anyone has had any success or failures with this approach? Does anyone even have a viable monitoring option so that at least we could determine how often and how long these outages last?

Thanks for any help!!

For anyone else who finds this down the road, we ended up using Code Blocks to replace all of Squarespace's forms with forms that link directly to our CRM.

I can't save my form - I get this error. Tried everything, starting over, using different storage, external link, link in Post-Submit box, etc. I get this error.

There has been an error in saving this form. 

Once I saved the page, then I got this where the form is supposed to be on the page. HELP!

Our system has encountered an error. This exception has been automatically logged and reported. 5FMFA76C5DA5RFLMS8K7